Isolated polypeptide of the toxin A and toxin B proteins of C. difficile and uses thereof

ABSTRACT

This present invention provides C-TAB.G5 and C-TAB.G5.1 isolated polypeptides comprising the receptor binding domains of C. difficile toxin A and toxin B as set forth in the amino acid sequences of SEQ ID NO: 2 and SEQ ID NO: 4. The C-TAB.G5 and C-TAB.G5.1 isolated polypeptides may be used to neutralize toxic effects of C. difficile toxin A and/or toxin B.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/061,891, filed Oct. 2, 2020, which is a continuation of U.S.application Ser. No. 16/295,031, filed Mar. 7, 2019, now issued as U.S.Pat. No. 10,821,166, which is a continuation of U.S. application Ser.No. 15/421,808, filed Feb. 1, 2017 and now issued as U.S. Pat. No.10,357,557, which is a division of U.S. application Ser. No. 14/342,565,filed Oct. 28, 2014 and now issued as U.S. Pat. No. 9,598,472, which isa national stage filing under 35 U.S.C. § 371 of internationalapplication PCT/EP2011/065304, filed Sep. 5, 2011, which was publishedunder PCT Article 21(2) in English, the disclosure of each of which isincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to an isolated polypeptide containing thereceptor binding domains of the Clostridium difficile toxin A and toxinB and its use as a vaccine. This isolated polypeptide providesanti-toxin immunity to both toxins.

BACKGROUND OF THE INVENTION

Clostridium difficile is the leading cause of nosocomial antibioticassociated diarrhea and has become a major health problem in hospitals,nursing home and other care facilities. The cost to hospitals has beenestimated to be 2 billion dollars in Europe and 3.2 billion dollars inthe United States.

The causative agent is a gram positive, spore forming anaerobicbacterium, commonly found through out the environment but also presentin the intestinal tract of 2-3% of the healthy adult population. C.difficile associated disease (CDAD) is induced by the disruption of thenormal colonic flora, usually the result of the administration ofantibiotics. Following exposure to C. difficile spores in theenvironment, the organism may colonize the intestinal mucosa where theproduction of disease causing toxins can result in CDAD. Disease mayrange from mild uncomplicated diarrhea to severe pseudomembranouscolitis and toxic megacolon.

CDAD has become increasingly more problematic in health care settings. Arecent study reported that 31% of hospital patients who receiveantibiotics become colonized with C. difficile and 56% of those patientswho become colonized go on to develop CDAD. Overall, C. difficile isresponsible for 10-25% of all antibiotic associated diarrheas, 50-75% ofantibiotic related colitis and 90-100% of antibiotic relatedpseudomembranous colitis. Treatment of CDAD involves discontinuation ofthe causal antibiotic followed by treatment with either metronidazole orvancomycin. Relapsing after antibiotic treatment is discontinued occursin approximately 20% of patients, often the result of recolonization byC. difficile.

In 2003, a C. difficile outbreak in Quebec, Canada indicated theemergence of a more virulent strain of C. difficile known as NorthAmerican Phenotype 1/027 (NAP1). NAP1 has been associated with greatervirulence, poor outcomes and greater morbidity and mortality ratescompared to previous strains. The emergence of this strain adds to theproblems already encountered in trying to contain the incidence of CDAD.

Fidaxomicin (Dificid®) for prevention of recurrent disease is the firstin a new class of narrow spectrum macrocyclic antibiotic drugs (Revill,P.; Serradell, N.; Bolos, J. (2006). “Tiacumicin B: macrolide antibiotictreatment of C. difficile-associated diarrhea”. Drugs of the Future 31(6): 494-497). It is a fermentation product obtained from theactinomycete Dactylosporangium aurantiacum subspecies hamdenesis.Fidaxomicin is non-systemic, meaning it is minimally absorbed into thebloodstream, it is bactericidal, and it has demonstrated selectiveeradication of pathogenic Clostridium difficile with minimal disruptionto the multiple species of bacteria that make up the normal, healthyintestinal flora. The maintenance of normal physiological conditions inthe colon can reduce the probability of Clostridium difficile infectionrecurrence (Johnson, Stuart (2009 June). “Recurrent Clostridiumdifficile infection: a review of risk factors, treatments, andoutcomes”. Journal of Infection 58 (6): 403-410). Although it isthought, that the introduction of this new class of antibiotic drug willimprove the treatment of CDAD, there is still a medical need for apreventative drug, in particular for high risk patients such as theelderly and the immunocompromised patients.

CDAD is the result of the actions of two exotoxins produced by C.difficile, toxin A and toxin B (also referred to as CTA and CTB,respectively). Both toxins are high molecular weight (˜300 kDa) secretedproteins that possess multiple functional domains (Voth D E and BallardJ D, Clinical Microbiology Reviews 18:247-263 (2005)). The N-terminaldomain of both toxins contains ADP-glucosyltransferase activity thatmodifies Rho-like GTPases. This modification causes a loss of actinpolymerization and cytoskeletal changes resulting in the disruption ofthe colonic epithelial tight junctions. This leads to excessive fluidexudation into the colon and a resulting diarrhea. The central domaincontains a hydrophobic domain and is predicted to be involved inmembrane transport. The C-terminal domain of both toxins containmultiple homologous regions called repeating units (RUs) that areinvolved in toxin binding to target cells (Ho et al, Howell102:18373-18378 (2005)). The repeating units are classified as eithershort (21-30 amino acids) or long (˜50 amino acids). Repeating unitscombine to form clusters, each usually containing one long and 3-5 shortrepeating units. The full length toxin A possesses 39 repeating units(ARUs) organized into 8 clusters (Dove et al. Infect. Immun. 58:480-488(1990), while the full length toxin B contains 24 repeating units (BRUs)organized into 5 clusters (Barroso et al., Nucleic Acids Res. 18:4004(1990); Eichel-Streiber et al., Gene 96:107-113 (1992)).

A number of studies, from both animal models and from the clinic, haveindicated a role for anti-toxin antibody in the protection from C.difficile associated disease. Hamsters immunized with formalininactivated toxin A and toxin B generated high levels of anti-toxinantibody and were protected from a lethal challenge of C. difficilebacteria (Giannasca P J and Warny M, Vaccine 22:848-856 (2004)). Inaddition, passive transfer of mouse anti-toxin antibody protectedhamsters in a dose dependent manner. Kyne L et al. (The Lancet357:189-193 (2001)) reported that the development of an anti-toxin Aantibody response during an initial episode of CDAD correlated withprotection against disease recurrence.

The determinants recognized by protective anti-toxin antibodies havebeen localized to the C-terminal domain containing the reating unitswhich function as the receptor binding domain. Initially, Lyerly et al.(Current Microbiology 21:29-32 (1990)) revealed that the toxin AC-terminal domain containing 33 repeating units is capable of inducingthe production of neutralizing anti-toxin antibody and may protect fromC. difficile infection. In this study hamsters were injectedsubcutaneously with the purified recombinant polypeptide multiple timesprior to challenge with the bacteria, however only partial protectionwas achieved. Another study (Ryan et al., Infect. Immun. 65:2941-49(1997)) showed that the isolated polypeptide containing 720 amino acidresidues from the C-terminus of CTA and the secretion signal of E. colihemolysin A (expressed in Vibrio cholerae) induced protective systemicand mucosal immunity against a small dose of CTA in the rabbit CDADmodel.

It was also reported that antibody response against the C-terminaldomain of both toxin A and B was necessary to achieve full protection(Kink and Williams, Infect. Immun. 66:2018-25 (1998), U.S. Pat. No.5,736,139 (1998)). This study revealed that the C-terminal domain ofeach toxin was most effective in generating toxin-neutralizingantibodies. It demonstrated the effectiveness of orally delivered avianantibodies (antitoxin) raised against C-terminal domain of CTA and CTBin the hamster lethal model. The results also indicate that theantitoxin may be effective in the treatment and management of CDAD inhumans. In another study, human anti-toxin A and B monoclonal antibodieswere reported confer protection against C. difficile induced mortalityin hamsters (Babcock et al., Infect. Immun. 74:6339-6347 (2006)).Protection was only observed by antibodies directed against the receptorbinding domain of either toxin and enhanced protection was observedfollowing treatment with both anti-toxin A and B antibodies.

On the other hand, Ward et al. (Infect. Immun. 67: 5124-32 (1999))considered 14 repeating units from C. difficile toxin A (14 CTA) for thestudy of adjuvant activity. The repeating units were cloned andexpressed either with the N-terminal polyhistidine tag (14 CTA-HIS) orfused to the nontoxic binding domain from tetanus toxin (14 CTA-TETC).Both fusion proteins administered intranasally generated anti-toxin Aserum antibodies but no response at the mucosal surface in mice.Enhanced systemic and mucosal anti-toxin A responses were seen followingco-administration with E. coli heat-labile toxin (LT) or its mutatedform LTR72. Based on the data, Ward et al. suggested using non-toxic 14CTA-TETC fusion as a mucosal adjuvant in human vaccine directed againstclostridial pathogens.

Recent biochemical studies on the repeating unit domains of C. difficiletoxins has looked at the minimal sequence requirements for formingstable tertiary structure (Demarest S J et al., J. Mol. Bio.346:1197-1206 (2005)). An 11 repeating unit peptide derived from toxin Awas found with a correct tertiary structure but 6 and 7 repeating unitsfrom toxins A and B did not. The correctly folded 11 repeating unitsegment was found to maintain the receptor binding property. A secondstudy examined the functional properties of toxin A fragments containing6, 11 or 15 repeating units (Dingle T, Glycobiology 18:698-706 (2008)).Only the 11 and 15 repeat units were capable of competitively inhibitingthe toxin neutralizing ability of anti-toxin A antibody. While all 3fragments were found to have hemagglutinating activity, the longerfragments displayed higher hemagglutinating activity than the shorterones. The data indicates that toxin receptor binding domain structureand immunogenicity are retained in domain fragments that contain greaterthan 11-14 repeats.

Thomas et al. (WO97/02836, U.S. Pat. No. 5,919,463 (1999)) alsodisclosed C. difficile toxin A, toxin B and certain fragments thereof(e.g., C-terminal domain containing some or all of the repeating units)as mucosal adjuvants. They showed that intranasal administration of CTAor CTB significantly enhanced mucosal immune response to a heterologousantigen such as Helicobacter pylori urease, ovalbumin, or keyhole limpethemocyanin (KLH) in multiple mouse compartments and was associated withprotection against the challenge with Helicobacter. Additionally, theadjuvant activity of a toxin A fusion protein was evaluated: 794C-terminal amino acid residues of CTA comprising ARUs (toxin A repeatingunits) were fused to glutatione-S-transferase (GST) and resultedpolypeptide GST-ARU was expressed in E. coli. This study demonstratedsignificant enhancement of immune response by GST-ARU to co-administeredantigens in serum and mucosal secretions.

All of these studies suggest potential use of a non-toxic, recombinantprotein comprising either C. difficile toxin A, or toxin B, or fragmentsthereof, or their combinations for producing an active vaccine againstCDAD. Currently, no vaccine against C. difficile is commerciallyavailable, although a candidate vaccine consisting offormalin-detoxified entire toxins A and B has been evaluated in humanphase I and IIa studies. It is reported that parenteral immunizationwith this vaccine induces anti-toxin IgG and toxin-neutralizing antibodyresponses (Kotloff K L et al., Infect. Immun. 69:988-995 (2001);Aboudola S et al., Infect. Immun. 71:1608-1610 (2003)).

The literature further indicates that the construction of a recombinantfusion protein containing both toxin A and B receptor binding domains ofC. difficile, either in their entirety or fragments thereof, would be anefficient and commercially viable approach for vaccine development. Suchan approach has been attempted as a two part fusion protein of a 700base pair fragment of toxin A and a 1300 base pair fragment of toxin Bby Varfolomeeva et al. (Mol. Genetics, Microb. and Virol. 3:6-10(2003)). This approach has also been described by Belyi and Varfolomeeva(FEMS Letters 225:325-9 (2003)) demonstrating construction of therecombinant fusion protein consisting of three parts: two C-terminaldomains composed of repeating units of C. difficile toxin A and toxin Bfollowed by the fragment of Clostridium perfringens enterotoxin Cpe. Thefusion protein was expressed in E. coli but the product was accumulatedin inclusion bodies and was not stable. Moreover, the yield of pureproduct achieved in this study (50 μg per 100 ml culture) wasconsiderably low.

Wilkins et al. (WO 00/61762, U.S. Pat. No. 6,733,760 (2004)) alsodescribed the use of recombinant C. difficile toxin A and B repeatingunits (recombinant ARU and recombinant BRU) and their polysaccharideconjugates for the preparation of a vaccine against CDAD. The resultingrecombinant ARU protein comprised 867 amino acid residues while therecombinant BRU protein contains 622 amino acids in length. Unlike thepreviously mentioned studies, this work demonstrated high-levelexpression of recombinant ARU and BRU soluble proteins in E. coli. Micevaccinated with recombinant ARU and with polysaccharide-conjugatedrecombinant ARU both mounted a high level of neutralizing anti-toxin Aantibodies and were highly protected against lethal challenge with C.difficile toxin A. In addition, Wilkins et al. suggested using arecombinant fusion protein consisting of both ARU and BRU for thepreparation of a vaccine.

There is an interest in developing a vaccine against CDAD. A recombinantfusion protein consisting of ARU and BRU may be potentially useful as avaccine.

SUMMARY OF THE INVENTION

The present invention provides new tools and methods for the design,production and use of the toxin A and toxin B from C. difficile. Thepresent invention provides an isolated polypeptide C-TAB comprising SEQID NO: 2 (C-TAB.G5) or a derivative thereof, SEQ ID NO: 4 (C-TAB.G5.1).The C-TAB.G5 or C-TAB.G5.1 comprises 19 repeating units of theC-terminal domain of toxin A fused to 23 repeating units of theC-terminal domain of toxin B. The present invention also includescompositions and formulations comprising the C-TAB.G5 or C-TAB.G5.1isolated polypeptide. The compositions or formulations may contain theisolated polypeptide, an additional antigen, an adjuvant, and/or anexcipient. Alternatively, the compositions or formulations may consistessentially of the isolated polypeptide without an adjuvant or otheractive ingredients (but optionally comprising an excipient such as acarrier, buffer and/or stabilizer). Moreover, the compositions orformulations of the invention may be administered concomitantly withother drugs such as an antibiotic in particular e.g. in subjects withrecurrent CDAD or in subjects requiring frequent and/or prolongedantibiotic use.

The present invention also provides a vaccine comprising the isolatedpolypeptide of the present invention. The vaccine may further comprisean adjuvant, such as such as alum, an adjuvant derived from anADP-ribosylating exotoxin or others. The vaccine may be administered ina one dose regimen, two dose regimen (administered e.g. within 3 to 20days, e.g. after 10 to 15 days of the first dose), three dose regimen(administered e.g. after about 7 days and about 21 days of the firstdose), or more than three dose regimen, preferably a two or three doseregimen, wherein the dose comprises a 20 μg to 200 μg amount of thepolypeptide of the invention.

The present invention provides a method of preventing, treating, oralleviating one or more symptoms of a disease, such as CDAD byadministering the isolated polypeptide of the invention to a subject inneed thereof. The C-TAB.G5 or C-TAB.G5.1 isolated polypeptide may beadministered to the subject intramuscularly or by other routes ofdelivery.

In one embodiment, the present invention provides a method of preventinga disease, such as CDAD by administering the isolated polypeptide of theinventions or a composition comprising said polypeptide to a subject atrisk of CDAD, such as e.g. a subject with the following profile: i) asubject with a weaker immune system such as e.g. an elderly subject(e.g. a subject above 65 years of age) or a subject below 2 years ofage; ii) an immunocompromised subject such as e.g. a subject with AIDS;iii) a subject taking or planning to take immunosuppressing drugs; iv) asubject with planned hospitalization or a subject that is in hospital;v) a subject in or expected to go to an intensive care unit (ICU); vi) asubject that is undergoing or is planning to undergo gastrointestinalsurgery; vii) a subject that is in or planning to go to a long-term caresuch as a nursing home; viii) a subject with co-morbidities requiringfrequent and/or prolonged antibiotic use; ix) a subject that is asubject with two or more of the above mentioned profiles, such as e.g.an elderly subject that is planning to undergo a gastrointestinalsurgery; x) a subject with inflammatory bowel disease; and/or xi) asubject with recurrent CDAD such as e.g. a subject having experiencedone or more episodes of CDAD.

In one embodiment, the invention provides methods of producing theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide. The C-TAB.G5 or C-TAB.G5.1isolated polypeptide may be produced from a nucleic acid encoding theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide using a bacterial expressionsystem, such as an E. coli expression system.

In one embodiment the present invention provides the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide wherein the 19 repeating units of toxinA are connected to the 23 repeating units of toxin B via a linkerconsisting of at least 4, 5, 6, 7, 8, 9, or 10 amino acid residues. Byway of example, the linker of the present invention may comprise thesequence RSMH (Arg-Ser-Met-His) (amino acids 439-442 of SEQ ID NO: 2 orSEQ ID NO: 4).

In another embodiment the invention provides a variant of the isolatedpolypeptide that comprises at least one mutation (e.g., insertion,substitution or deletion), for example in the ARU and/or BRU. Thesequence of the variant may have 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%,93%, 94%, 95%, 96%, 97%, 98%, or 99% identity to SEQ ID NO: 2.

This invention also provides methods for producing the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide or variants thereof through recombinantDNA engineering, bacterial fermentation and protein purification. In oneembodiment, the present invention provides methods for constructing thenucleic acid encoding the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide.In another embodiment, the invention provides methods of producing theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide using a bacterial expressionsystem, such as an E. coli expression system.

The invention further provides methods for preventing and treating CDADin subjects in need thereof, such as humans. In this method the C-TAB.G5or C-TAB.G5.1 is administered to a subject either alone orco-administered with one or more adjuvants such as alum or others.Subjects may be healthy individuals who are at risk for exposure to C.difficile, human subjects who have been treated and recovered from C.difficile infection and who are at risk for re-infection by C.difficile, or human subjects who are currently infected with C.difficile and whose condition may be improved by induction of C.difficile toxin-neutralizing antibody.

The present invention provides an immunogenic composition comprisingC-TAB.G5 or C-TAB.G5.1. The immunogenic composition may further includean adjuvant to enhance an antigen-specific immune response and/or apharmaceutically acceptable carrier and/or other components in aformulation suitable for application to a subject in need thereof. Theimmunogenic composition may be delivered by intramuscular (IM) delivery,intradermal (ID) delivery, subcutaneous (SC) delivery, intraperitoneal(IP) delivery, oral delivery, nasal delivery, buccal delivery, or rectaldelivery.

In another embodiment of the invention the immunogenic compositionelicits antibodies that bind native C. difficile toxins and neutralizetheir cytotoxic activity thus providing long-term, active protection,and/or treatment against C. difficile associated disease (CDAD).

Accordingly, the invention provides immunogenic compositions useful forthe prevention or treatment of C. difficile associated disease insubjects in need thereof.

In another embodiment, the invention provides nucleic acids andfragments or variants thereof that encode C-TAB.G5 or C-TAB.G5.1. Theinvention also provides expression vectors comprising the nucleic acidencoding C-TAB.G5 or C-TAB.G5.1.

Another embodiment of the present invention provides antibodies andfragments thereof, such as neutralizing, humanized, monoclonal, chimericand polyclonal antibodies, specific for C-TAB.G5 or C-TAB.G5.1. Theantibodies or fragments thereof may recognize toxin A and/or toxin B.

Another embodiment provides a vaccine comprising a polypeptide havingthe amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 4.

Another embodiment of this invention provides diagnostic kits comprisingthe nucleic acids, polypeptides and/or antibodies of the invention.

Other embodiments and advantages of the invention are set forth in partin the description, which follows, and in part, may be obvious from thisdescription, or may be learned from the practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows the nucleic acid encoding the C-TAB.G5 isolatedpolypeptide (SEQ ID NO: 1). FIG. 1B shows the amino acid sequence of theC-TAB.G5 isolated polypeptide (SEQ ID NO: 2). The amino acid linkerbetween the toxin A domain and the toxin B domain is underlined.

FIG. 2A shows the nucleic acid encoding the C-TAB.G5.1 isolatedpolypeptide (SEQ ID NO: 3). FIG. 2B shows the amino acid sequence of theC-TAB.G5.1 isolated polypeptide (SEQ ID NO: 4). The amino acid linkerbetween the toxin A domain and the toxin B domain is underlined.

FIG. 3 shows the enhancement of antibody production in C-TAB.G5vaccinated mice by increasing doses of C-TAB.G5 and co-delivery withalum adjuvant. Mice received two vaccinations by IM injection. IgGtiters for anti-C-TAB, anti-toxin A and anti-toxin B antibodies wereevaluated by ELISA two weeks after the first and second injection.

FIG. 4 shows a graphical representation of anti-C-TAB, anti-toxin A, andanti-toxin B IgG induction in mice receiving increasing doses ofC-TAB.G5 with and without alum by two IM injection.

FIG. 5 shows antibody titers over one log dose range in mice immunizedwith C-TAB.G5 in the presence or absence of alum. IgG titers wereevaluated by ELISA two weeks after the second immunization. The datademonstrate that alum significantly augments antibody production invaccinated mice.

FIG. 6 shows protective effect in mice vaccinated with C-TAB.G5 (withand without alum) and then exposed to a lethal dose of toxin A or toxinB. Mice receiving two vaccinations (IM) in two week interval werechallenged (IP) three weeks later. Toxin A and toxin B neutralizingantibodies (TNA) were assessed two weeks after the second injection, andthe percent of animals survived the lethal challenge was determined.Increased doses of C-TAB.G5 conferred greater TNA production, as well asincreased protection to the lethal challenge. The presence of alumfurther increased TNA production, as well as conferring higher survivalat lower doses.

FIG. 7 shows a comparison of antibody response and protection efficacyof C-TAB.G5 in vaccinated young (6-7 weeks) and old (18 months) mice.Mice receiving two vaccinations (IM) in two week interval werechallenged (IP) three weeks later. ELISA IgG titers for anti-C-TAB,anti-toxin A and anti-toxin B antibodies, TNA production as well asoverall survival were assessed. Young mice demonstrated higher antibodyresponse even without alum, and both groups showed improved survivalwhen vaccinated in the presence of alum.

FIG. 8 shows a comparison of the kinetics of anti-C-TAB IgG antibodydevelopment in vaccinated young and old mice. Young mice demonstratedgreater rates and earlier IgG production, and both groups demonstratedimproved responses when vaccinated in the presence of alum.

FIG. 9 shows a comparison in anti-C-TAB, anti-toxin A and anti-toxin Bantibody production in mice immunized with either C-TAB.G5.1 or toxoid Aand B mixture (1:1). Mice received two vaccinations IM injection. IgGtiters for anti-C-TAB, anti-toxin A and anti-toxin B antibodies wereevaluated by ELISA two weeks after the second injection. Immunizationwith toxoid induces antibody to the N-terminal portion of the toxinmolecule while immunization with C-TAB induces antibody to theC-terminal portion of the toxin molecule.

FIG. 10 shows a comparison in TNA production and protection againstchallenge with toxin A or B in mice immunized with either C-TAB.G5.1 ortoxoid A and B mixture. Mice receiving two vaccinations (IM) in two weekinterval were challenged (IP) three weeks later with a lethal dose oftoxin A or toxin B.

FIGS. 11A-11C show anti-C-TAB (FIG. 11A), anti-toxin A (FIG. 11B), andanti-toxin B (FIG. 11C) IgG production in hamsters immunized withC-TAB.G5.1 with and without alum. Hamsters received three vaccinationsby IM injection on day 0 and day 14. IgG titers for anti-C-TAB,anti-toxin A and anti-toxin B antibodies were evaluated by ELISA on days14, 28 and 35.

FIG. 12 shows a graphical representation of anti-C-TAB IgG antibodydevelopment in hamsters immunized with C-TAB.G5.1 with or without alum.

FIG. 13 shows a comparison in TNA and protection in hamsters immunizedwith C-TAB.G5.1 with or without alum. Two weeks after the thirdvaccination hamsters received a lethal dose of toxin A or toxin B by IPinjection.

FIG. 14 shows survival of hamsters vaccinated with C-TAB.G5.1 followingthe intragastric administration of a lethal dose of C. difficile spores.Survival data was plotted as Kaplan-Meier survival fit curves andstatistical analysis was done using a log rank analysis. At all sporedoses (10², 10³ and 10⁴), 100% survival of hamsters in the vaccinatedgroup was observed and survival was significantly enhanced when comparedto the placebo group.

FIG. 15 shows anti-C-TAB, anti-toxin A, and anti-toxin B antibodyproduction in cynomolgous monkeys immunized with C-TAB.G5.1 in thepresence or absence of alum. Two groups of monkeys (three per group, 4-6years) received 200 μg of C-TAB.G5.1 with or without 250 μg alum. Bloodsamples were taken on study days 0, 14, 28 and 42. ELISA method was usedto assess anti-C-TAB, anti-toxin A and anti-toxin B IgG titers.

FIG. 16 shows a comparison of immunogenicity of C-TAB.G5 and C-TAB.G5.1delivered over a 1 μg-30 μg dose range either in PBS or histidinebuffer. Mice received two vaccinations (IM) in two week interval. IgGtiters for anti-C-TAB, anti-toxin A and anti-toxin B antibodies wereevaluated by ELISA two weeks after the second injection. All threeantibody titers were not significantly different (T-test analysis)between C-TAB.G5 delivered in PBS or histidine buffer and C-TAB.G5.1delivered in histidine buffer.

FIG. 17 shows a comparison of immunogenicity of C-TAB.G5, C-TABNCTB andC-TADCTB in mice. Mice received two vaccinations of each recombinantprotein in two week interval by IM injection. All immunizations weredone in the absence of alum adjuvant. IgG titers for anti-C-TAB,anti-toxin A and anti-toxin B antibodies were evaluated by ELISA twoweeks after the second injection. All three fusion proteins demonstratehigh immunogenicity.

FIG. 18 shows protection against challenge with native toxin B in mice.Mice were immunized as indicated for FIG. 17 and three weeks later theywere challenged by IP injection with a lethal dose of native toxin B.

FIG. 19 shows a comparison in TNA and protection in hamsters vaccinatedwith either C-TAB.G5.1 or C-TADCTB in the absence or presence of alum.Two weeks after the third vaccination hamsters received a lethal dose oftoxin A or toxin B by IP injection.

FIGS. 20A and 20B show TNA production and protection against challengewith toxin A or toxin B in mice immunized with C-TAB.G5.1 in differentregimens. Comparison in TNA production and protection between groups ofmice vaccinated by IM injection three times on day 0, 3 and 14, or onday 0, 7 and 21, or on day 0, 14 and 28. Three weeks after the lastinjection mice were challenged with a lethal dose of toxin A or toxin B(FIG. 20A is in table form and FIG. 20B is in graph form).

FIG. 21 shows protection (survival) against challenge with C. difficiletoxin A (55 ng/mouse) in mice immunized with a single shot of 10 μgC-TAB.G5.1 and 12.5 μg alum (in 100 μl). Said challenge was done 21days, 35 days or 49 days after immunization.

DETAILED DESCRIPTION

General Description

The present invention provides an immunogenic composition for inducingprotective and/or therapeutic immune responses to C. difficile toxins Aand B comprising use of a isolated polypeptide C-TAB.G5 (SEQ ID NO: 2)or a derivative thereof, C-TAB.G5.1 (SEQ ID NO: 4). that comprises 19repeating units (RU) of toxin A and 23 repeating units (RU) of toxin Bor peptide fragments, or variants thereof.

The present invention also provides methods of producing the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide and the method of preparing thecomposition (e.g. a vaccine) useful for prevention and/or treatment ofCDAD in mammals. The following description provides more details andexamples for the construction, expression, and purification of therecombinant isolated polypeptides, their use as antigens for inducing aspecific-immune response as well as evaluating protection in subjects.The subjects may be animals or humans.

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides for use in the methodsand compositions of the present invention may be prepared using any ofseveral standard methods. For example, the C-TAB.G5 or C-TAB.G5.1 may beproduced using standard recombinant DNA techniques, wherein a suitablehost cell is transformed with an appropriate expression vectorcontaining a part of a toxin-encoding nucleic acid fragment (see e.g.Dove et al., Infect. Immun. 58:480-8 (1990), and Barroso et al., NucleicAcids Research 18:4004 (1990). Any of a wide variety of expressionsystems may be used to produce the recombinant polypeptides. C-TAB.G5 orC-TAB.G5.1 may be produced in a prokaryotic host (e.g. a bacterium, suchas E. coli or Bacillus) or in an eukaryotic host (e.g. yeast cells,mammalian cells (e.g. COS1, NIH3T3, or JEG3 cells), or insect cells(e.g. Spodoptera frugiperda (SF9) cells)). Such cells are available, forexample, from the American Type Culture Collection (ATCC). The method oftransformation and transfection and the choice of expression vector willdepend on the host system selected. Transformation and transfectionmethods are described by, e.g., Ausubel et al., ISBN: 047132938XC-TAB.G5 or C-TAB.G5.1, particularly short fragments, may also beproduced by chemical synthesis, e.g., by the methods described in SolidPhase Peptide Synthesis, 1984, 2nd ed., Stewart and Young, Eds., PierceChemical Co., Rockford, Ill., or by standard in vitro translationmethods.

In addition to the C-TAB.G5 or C-TAB.G5.1 sequences, the presentinvention provides variants thereof that are functionally active andimmunogenic. The variants may have the same level of immunogenicity asC-TAB.G5 or C-TAB.G5.1. The variant may have amino acid substitutions,deletions, or insertions as compared to SEQ ID NO: 2 or SEQ ID NO: 4.Genes encoding C-TAB.G5 or C-TAB.G5.1 or variants thereof may be madeusing standard methods (see below; also see, e.g. Ausubel et al.,supra).

In addition to the C-TAB.G5 or C-TAB.G5.1 sequences, the presentinvention provides further derivatives of C-TAB.G5 that compriseadditional repeats. By way of example, a fusion protein, C-TABNCTB (SEQID NO: 18, encoded by SEQ ID NO: 17), comprises, like C-TAB.G5, 19repeating units of CTA (amino acids 2272-2710), 23 repeating units ofCTB (amino acids 1850-2366), and a further additional 10 repeats of CTB(amino acids 1834-2057) fused to the C-terminus of CTB. A furthervariant, C-TADCTB fusion protein (SEQ ID NO: 20, encoded by SEQ IDNO:19) comprises C-TAB.G5 (19 repeats of CTA and 23 repeats of CTB) plusan additional 24 repeating units of CTB (amino acids 1834-2366) fused tothe C-terminus of C-TAB.G5. A variant may also comprise additionalcopies of C-TAB.G5 or portions thereof. For example, C-TADCTB comprisesa double portion of the repeating units of CTB present in C-TAB.G5.

The present invention provides methods for high level expressionC-TAB.G5 or C-TAB.G5.1 in bacterial system such as E. coli comprisingintroducing a nucleic acid encoding C-TAB.G5 or C-TAB.G5.1 into abacterial host cell and expressing C-TAB.G5 or C-TAB.G5.1.

In addition, the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide of thepresent invention may be covalently coupled or cross-linked to adjuvants(see, e.g., Cryz et al., Vaccine 13:67-71 (1994); Liang et al., J.Immunology 141:1495-501 (1988) and Czerkinsky et al., Infect. Immun.57:1072-77 (1989)).

The present invention provides a vaccine comprising the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide that can protect and provide therapyagainst CDAD. The vaccine of the present invention comprises a novelantigen which can be delivered intramuscularly (IM), intradermally (ID),subcutaneously (SC), orally, nasally, buccally, or rectally routes. Thevaccine may provide immune protection or induce antibodies for passiveimmunization.

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptide of the present inventionprovides a vaccine to immunize against CDAD. The C-TAB.G5 or C-TAB.G5.1isolated polypeptide of the present invention or variants thereof, is acombined vaccine candidate targeted to broaden the protective coverageagainst C. difficile associated diseases, such as CDAD, to a level notknown or published hitherto. This concept of a single vaccine offeringprotection or a diminished severity of C. difficile associated diseasesrepresents a unique step forward in managing public health at a globallevel and especially reducing the severity of epidemics (e.g. nursinghomes, cruise ships).

As used herein, “toxin A protein” or “toxin B protein” refers to toxicproteins of C. difficile that are primarily responsible for CDAD. ToxinA and toxin B comprise multiple repeating units responsible forimmunogenicity in the C-terminal binding domains.

As used herein “wild-type” or “native” refers to a full length proteincomprised of a nucleic acid or amino acid sequence as would be foundendogenously in a host cell.

As used herein, the terms “Clostridium difficile associated disease”,“Clostridium difficile related disease”, “Clostridiumdifficile-associated disease”, “Clostridium difficile toxin-mediateddisease”, “Clostridium difficile infection”, and “CDAD” refer todiseases caused, directly or indirectly, by infection with Clostridiumdifficile.

“Antigen” refers to a substance that induces a specific immune responsewhen presented to immune cells of an organism. For example, an antigenmay be a nucleic acid, a protein, a polypeptide, a peptide, aglycoprotein, a carbohydrate, a lipid, a glycolipid, a lipoprotein, afusion protein, a phospholipid, or a conjugate of a combination thereof.An antigen may comprise a single immunogenic epitope, or a multiplicityof immunogenic epitopes recognized by a B-cell receptor (i.e., antibodyon the membrane of the B cell) or a T-cell receptor. Antigen may beprovided as a virus-like-particle (VLP) or a whole microbe ormicroorganism such as, for example, a bacterium or virion. The antigenmay be an inactivated or attenuated live virus. The antigen may beobtained from an extract or lysate, either from whole cells or membranealone; or antigen may be chemically synthesized or produced byrecombinant means. An antigen may be administered by itself or with anadjuvant. A single antigen molecule may have both antigen and adjuvantproperties.

By “adjuvant” is meant any substance that is used to specifically ornon-specifically potentiate an antigen-specific immune response, perhapsthrough activation of antigen presenting cells. Examples of adjuvantsinclude an oil emulsion (e.g., complete or incomplete Freund'sadjuvant), Montanide incomplete Seppic adjuvant such as ISA, oil inwater emulsion adjuvants such as the Ribi adjuvant system, syntaxadjuvant formulation containing muramyl dipeptide, aluminum saltadjuvant (ALUM), polycationic polymer, especially polycationic peptide,especially polyarginine or a peptide containing at least two LysLeuLysmotifs, especially KLKLLLLLKLK (SEQ ID NO: 21), immunostimulatoryoligodeoxynucleotide (ODN) containing non-methylated cytosine-guaninedinucleotides (CpG) in a defined base context (e.g., as described in WO96/02555) or ODNs based on inosine and cytidine (e.g., as described inWO 01/93903), or deoxynucleic acid containing deoxy-inosine and/ordeoxyuridine residues (as described in WO 01/93905 and WO 02/095027),especially Oligo(dIdC)₁₃ (as described in WO 01/93903 and WO 01/93905),neuroactive compound, especially human growth hormone (described in WO01/24822), or combinations thereof, a chemokine (e.g., defensins 1 or 2,RANTES, MIP1-α, MIP-2, interleukin-8, or a cytokine (e.g.,interleukin-1β, -2, -6, -10 or -12; interferon-γ; tumor necrosisfactor-α; or granulocyte-monocyte-colony stimulating factor) (reviewedin Nohria and Rubin, 1994), a muramyl dipeptide variant (e.g.,murabutide, threonyl-MDP or muramyl tripeptide), synthetic variants ofMDP, a heat shock protein or a variant, a variant of Leishmania majorLeIF (Skeiky et al., 1995, J. Exp. Med. 181: 1527-1537), non-toxicvariants of bacterial ADP-ribosylating exotoxins (bAREs) includingvariants at the trypsin cleavage site (Dickenson and Clements, (1995)Infection and Immunity 63 (5): 1617-1623) and/or affectingADP-ribosylation (Douce et al., 1997) or chemically detoxified bAREs(toxoids), QS21, Quill A,N-acetylmuramyl-L-alanyl-D-isoglutamyl-L-alanine-2-[1,2-dipalmitoyl-s-glycero-3-(hydroxyphosphoryloxy)]ethylamide(MTP-PE) and compositions containing a metabolizable oil and anemulsifying agent. An adjuvant may be administered with an antigen ormay be administered by itself, either by the same route as that of theantigen or by a different route than that of the antigen. A singleadjuvant molecule may have both adjuvant and antigen properties.

By “effective amount” is meant an amount of a therapeutic agentsufficient to induce or enhance an antigen-specific immune response, foran antigen, or treat or diagnose a condition, for a drug. Such inductionof an immune response may provide a treatment such as, for example,immunoprotection, desensitization, immunosuppression, modulation ofautoimmune disease, potentiation of cancer immunosurveillance, ortherapeutic vaccination against an established infectious disease.Treatment includes curing, amelioration, or prevention.

By “nucleic acid” is meant either a single deoxyribonucleic acid base ora ribonucleic acid or a sequence thereof joined by phosphodiester bonds.

By “therapeutic agent” is meant any molecule capable of use in treatinga disease, alleviating the symptoms of a disease, preventing a disease,or diagnosing a disease. For example, a therapeutic agent may be anantigen or a drug.

By “subject” is meant an animal. The subject may be any animal,including any vertebrate. The subject may be a domestic livestock,laboratory animal (including but not limited to, rodents such as a rat,hamster, gerbil, or mouse) or pet animal. In one embodiment, the animalmay be a mammal. Examples of mammals include humans, primates,marsupials, canines, monkeys, rodents, felines, apes, whales, dolphins,cows, pigs, and horses. The subject may be in need of treatment of adisease or may be in need of a prophylactic treatment.

As used herein, the term “antibody” means an immunoglobulin molecule ora fragment of an immunoglobulin molecule having the ability tospecifically bind to a particular antigen. Antibodies are well known tothose of ordinary skill in the science of immunology. As used herein,the term “antibody” means not only full-length antibody molecules butalso fragments of antibody molecules retaining antigen binding ability.Such fragments are also well known in the art and are regularly employedboth in vitro and in vivo. In particular, as used herein, the term“antibody” means not only full-length immunoglobulin molecules but alsoantigen binding active fragments such as the well-known active fragmentsF(ab′)2, Fab, Fv, and Fd.

As used herein, the term “variants” may include proteins and/orpolypeptides and/or peptides that are different from a wild-typepolypeptide, wherein one or more residues have been conservativelysubstituted with a functionally similar residue, and further whichdisplays substantially identical functional properties of the wild-typepolypeptide. Examples of conservative substitutions include substitutionof one non-polar (hydrophobic) residue for another (e.g. isoleucine,valine, leucine or methionine) for another, substitution of one polar(hydrophilic) residue for another (e.g. between arginine and lysine,between glutamine and asparagine, between glycine and serine),substitution of one basic residue for another (e.g. lysine, arginine orhistidine), or substitution of one acidic residue for another (e.g.aspartic acid or glutamic acid). A variant may include any polypeptidehaving a tertiary structure substantially identical to a polypeptide ofthe invention which also displays the functional properties of thepolypeptides as described herein. A variant may be a mutant of awild-type polypeptide.

As used herein “treatment” may include any type of intervention used inan attempt to alter the natural course of the individual or cell.Treatment may include, but is not limited to, administration of e.g., apharmaceutical composition, alone or in combination with other treatmentmodalities generally known in the art. The “treatment” may be performedprophylactically, or subsequent to the initiation of a pathologic event.

As used herein, “pharmaceutically acceptable carrier” may include anymaterial which, when combined with an active ingredient, allows theingredient to retain biological activity and is non-reactive with thesubject's immune system. The pharmaceutically acceptable carriers and/orexcipients may include buffers, stabilizers, diluents, preservatives,and solubilizers. In general, the nature of the carrier or excipientswill depend on the particular mode of administration being employed. Forinstance, parenteral formulations usually comprise injectable fluidsthat include pharmaceutically and physiologically acceptable fluids suchas water, physiological saline, balanced salt solutions, aqueousdextrose, glycerol or the like as a vehicle. For solid compositions (e.g. powder, pill, tablet, or capsule forms), conventional non-toxic solidcarriers can include, for example, pharmaceutical grades of mannitol,lactose, starch, or magnesium stearate. In addition to biologicallyneutral carriers, pharmaceutical compositions to be administered cancontain minor amounts of non-toxic auxiliary substances, such as wettingor emulsifying agents, preservatives, and pH buffering agents and thelike, for example sodium acetate or sorbitan monolaurate.

As used herein, “fusion” may refer to nucleic acids and polypeptidesthat comprise sequences that are not found naturally associated witheach other in the order or context in which they are placed according tothe present invention. A fusion nucleic acid or polypeptide does notnecessarily comprise the natural sequence of the nucleic acid orpolypeptide in its entirety. Fusion proteins have the two or moresegments joined together through normal peptide bonds. Fusion nucleicacids have the two or more segments joined together through normalphosphodiester bonds.

Isolated Polypeptides

The present invention provides the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptides as set forth in SEQ ID NO: 2 and SEQ ID NO: 4,respectively, that comprises 19 repeating units of C. difficile toxin Aand 23 repeating units of C. difficile toxin B. A homolog of C-TAB.G5,such as C-TAB.G5.1, may differ from C-TAB.G5 by 1, 2, 3, 4, 5, 6, 7, 8,9, or 10 amino acids. The C-TAB.G5.1 polypeptide is a fusion proteincontaining the same C-terminal domain of toxin B as C-TAB.G5, but theC-terminal domain of toxin A derived from C. difficile VPI-10463 strainwhich is a homolog of the according C-TAB.G5 polypeptide derived from C.difficile 630 strain and differs by two amino acids at positions155-156. The C-TAB.G5.1 coding sequence, as set forth in SEQ ID NO: 3,was codon optimized for improved expression within an E. coli host cell.The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides of the presentinvention may be effective in neutralizing the toxic effects of C.difficile toxin A and toxin B.

Toxin A and toxin B are encoded by the trdA (SEQ ID NO: 5) and trdB (SEQID NO: 7) genes, of the C. difficile strain 630, respectively.Structurally, the C. difficile toxins comprise an ADP-glucosyltransferase domain, a cysteine protease domain, a hydrophobic region,and a receptor binding region. The C-terminal domain contains highlyrepetitive units (RUs) (also known as combined repetitive oligopeptides(CROPS)). The RUs may be long or short oligopeptides and may comprise 20to 50 amino acids with a consensus YYF motif that is repeated. The RUsare grouped in clusters. As an example, toxin A, strain 630 (SEQ ID NO:6) encoded by the wild-type trdA gene (SEQ ID NO: 5) contains 39 RUs.The 39 RUs are grouped into 8 clusters. Toxin B, strain 630 (SEQ ID NO:8) encoded by the wild-type trdB gene (SEQ ID NO: 7) contains 24 RUswhich are grouped into 5 clusters. Tables 1 and 2 below show the aminoacid positions of each of the RUs in C. difficile toxin A and toxin Bencoded by the trdA gene and trdB gene.

TABLE 1 Toxin A Repeating Units (ARU) AA AA START END (SEQ (SEQ ID IDCLUSTER REPEAT NO: 6) NO: 6) SEQ 1 S1 1832 1852 GLININNSLFYFDPIEFNLVT S11853 1873 GWQTINGKKYYFDINTGAALI S3 1874 1893 SYKIINGKHFYFNNDGVMQL L 18941924 GVFKGPDGFEYFAPANTQNNN IEGQAIVYQS 2 S1 1925 1944KFLTLNGKKYYFDNNSKAVT S2 1945 1965 GWRIINNEKYYFNPNNAIAAV S3 1966 1986GLQVIDNNKYYFNPDTAIISK S4 1987 2007 GWQTVNGSRYYFDTDTAIAFN S5 2008 2027GYKTIDGKHFYFDSDCVVKI L 2028 2058 GVFSTSNGFEYFAPANTYNNN IEGQAIVYQS 3 S12059 2078 KFLTLNGKKYYFDNNSKAVT S2 2079 2099 GWQTIDSKKYYFNTNTAEAAT S32100 2120 GWQTIDGKKYYFNTNTAEAAT S4 2121 2141 GWQTIDGKKYYFNTNTAIAST S52142 2161 GYTIINGKHFYFNTDGIMQI L 2162 2192 GVFKGPNGFEYFAPANTDANNIEGQAILYQN 4 S1 2193 2212 EFLTLNGKKYYFGSDSKAVT S2 2213 2233GWRIINNKKYYFNPNNAIAAI S3 2234 2253 HLCTINNDKYYFSYDGILQN S4 2254 2275GYITIERNNFYFDANNESKMV T L 2276 2306 GVFKGPNGFEYFAPANTHNNN IEGQAIVYQN 5S1 2307 2326 KFLTLNGKKYYFDNDSKAVT S2 2328 2347 GWQTIDGKKYYFNLNTAEAAT S32348 2368 GWQTIDGKKYYFNLNTAEAAT S4 2369 2389 GWQTIDGKKYYFNTNTFIAST S52390 2409 GYTSINGKHFYFNTDGIMQI L 2410 2440 GVFKGPNGFEYFAPANTDANNIEGQAILYQN 6 S1 2441 2460 KFLTLNGKKYYFGSDSKAVT S2 2461 2481GLRTIDGKKYYFNTNTAVAVT S3 2482 2502 GWQTINGKKYYFNTNTSIAST S4 2503 2522GYTIISGKHFYFNTDGIMQI L 2523 2553 GVFKGPDGFEYFAPANTDANN IEGQAIRYQN 7 S12554 2573 RFLYLHDNIYYFGNNSKAAT S1 2574 2594 GWVTIDGNRYYFEPNTAMGAN S32595 2613 GYKTIDNKNFYFRNGLPQI L 2614 2644 GVFKGSNGFEYFAPANTDANNIEGQAIRYQN 8 S1 2645 2664 RFLHLLGKIYYFGNNSKAVT S2 2665 2686GWQTINGKVYYFMPDTAMAAA G S3 2687 2670 GLFEIDGVIYFFGVDGVKAPG IYG S:indicates a Short repeating unit L: indicates a Long repeating unit

TABLE 2 Toxin B Repeating Units (BRU) AA AA START END (SEQ (SEQ ID IDCLUSTER REPEAT NO: 8) NO: 8) SEQ 1 S1 1834 1854 GLIYINDSLYYFKPPVNNLIT S21855 1876 GFVTVGDDKYYFNPINGGAAS I S3 1877 1896 GETIIDDKNYYFNQSGVLQT L1897 1926 GVFSTEDGFKYFAPANTLDEN LEGEAIDFT 2 S1 1927 1946GKLIIDENIYYFDDNYRGAV S2 1947 1967 EWKELDGEMHYFSPETGKAFK S3 1968 1987GLNQIGDYKYYSNSDGVMQK S4 1988 2007 GFVNINDKTFYFDDSGVMKS S5 2008 2027GYTEIDGKHFYFAENGEMQI L 2028 2057 GVFNTEDGFKYFAHHNEDLGN EEGEEISYS 3 S12058 2078 GILNFNNKIYYFDDSFTAVVG S2 2079 2099 WKDLEDGSKYYFDEDTAEAYI S32100 2119 GLSLINDGQYYFNDDGIMQV S4 2120 2139 GFVTINDKVFYFSDSGIIES S5 21402159 GVQNIDDNYFYIDDNGIVQI L 2160 2189 GVFDTSDGYKYFAPANTVNDN IYGQAVEYS 4S1 2190 2212 GLVRVGEDVYYFGETYTIETG WI S2 2213 2233 YDMENESDKYYFNPETKKACKS3 2234 2253 GINLIDDIKYYFDEKGIMRT S4 2254 2273 GLISFENNNYYFNENGEMQF S52274 2293 GYINIEDKMFYFGEDGVMQI L 2294 2323 GVFNTPDGFKYFAHQNTLDENFEGESINYT 5 S1 2324 2343 GWLDLDEKRYYFTDEYIAAT S2 2344 2366GSVIIDGEEYYFDPDTAQLVI SE S: indicates a Short repeating unit L:indicates a Long repeating unit

Accordingly, the C-TAB.G5 and C-TAB.G5.1 isolated polypeptides comprises19 RUs from the C-terminal domain of C. difficile toxin A and 23 RUsfrom the C-terminal domain of C. difficile toxin B, respectively. TheC-TAB.G5 or C-TAB.G5.1 comprises toxin A amino acids 2272-2710 of SEQ IDNO: 6 fused to toxin B amino acids 1850-2366 of SEQ ID NO: 8. TheC-TAB.G5 or C-TAB.G5.1 isolated polypeptide comprises the amino acidsequence as set forth in SEQ ID NO: 2 and SEQ ID NO: 4, respectively.

The respective RUs in the C-TAB.G5 or C-TAB.G5.1 isolated polypeptidemay also be from variants of C. difficile toxin A or toxin B. These RUsin the C-TAB isolated polypeptide may also be a combination of naturallyoccurring or variants of C. difficile toxin A or toxin B.

The RUs in the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides compriselong RUs and short RUs, and the long RUs and the short RUs are arrangedinto a cluster. The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides of thepresent invention comprises 4 clusters of 3 to 5 short RUs followed byone long RU of C. difficile toxin A and 5 clusters of 3 to 5 short RUsfollowed by one long RU of C. difficile toxin B.

The short and long RUs contain conserved motifs. The short repeatingunit may comprise 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or 26amino acids. Each short repeating unit may comprise conserved tyrosinemotifs, such as YYF, FYF, YFF, FYI, or HYF. A short repeat unit mayfurther comprise an aspartate/histidine residue prior to the tyrosinemotif if the following repeating unit is a long repeating unit. The longrepeating unit may comprise 27, 28, 29, 30, 31, 32, 33, 34, or 35 aminoacids. Each long repeating unit may comprise a tyrosine repeat motifsuch as FEYF (SEQ ID NO: 22), FKYF (SEQ ID NO: 23), or YKYF (SEQ ID NO:24).

In the present invention, the toxin A and toxin B portions of theC-TAB.G5 or C-TAB.G5.1 isolated polypeptides may be fused directlytogether. The toxin A and toxin B portions may be spaced apart by alinker region. A linker region may comprise 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11 to 15, 20 to 30, 40, 45, or 50 amino acids. Those skilled in theart will recognize that the linker region may be adapted to alter thepositioning of the toxin A and toxin B portions so that in theirexpressed and folded shape each toxin repeating unit in the C-TAB.G5 orC-TAB.G5.1 isolated polypeptides is positioned to optimally exposepotential epitopes and to retain its immunogenicity. The RUs and theclusters in the C-TAB isolated polypeptides may also be separated bylinkers. In one embodiment, the linker comprises the peptide RSMH(439-442 of SEQ ID NO: 2 or SEQ ID NO: 4).

The C-TAB isolated polypeptides of the present invention may have atleast 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%,98%, or 99% sequence identity or sequence similarity with SEQ ID NO: 2or SEQ ID NO: 4. As known in the art “similarity” between twopolypeptides or polynucleotides is determined by comparing the aminoacid or nucleotide sequence and its conserved nucleotide or amino acidsubstitutes of one polynucleotide or polypeptide to the sequence of asecond polynucleotide or polypeptide. Also known in the art is“identity” which means the degree of sequence relatedness between twopolypeptide or two polynucleotide sequences as determined by theidentity of the match between two strings of such sequences. Bothidentity and similarity can be readily calculated (ComputationalMolecular Biology, Lesk, A. M., ed., Oxford University Press, New York,1988; Biocomputing: Informatics and Genome Projects, Smith, D. W., ed.,Academic Press, New York, 1993; Computer Analysis of Sequence Data, PartI, Griffin, A. M., and Griffin, H. G., eds., Humana Press, New Jersey,1994; Sequence Analysis in Molecular Biology, von Heinje, G., AcademicPress, 1987; and Sequence Analysis Primer, Gribskov, M. and Devereux,J., eds., M Stockton Press, New York, 1991). While there exist a numberof methods to measure identity and similarity between two polynucleotideor polypeptide sequences, the terms “identity” and “similarity” are wellknown to skilled artisans (Sequence Analysis in Molecular Biology, vonHeinje, G., Academic Press, 1987; Sequence Analysis Primer, Gribskov, M.and Devereux, J., eds., M Stockton Press, New York, 1991; and Carillo,H., and Lipman, D., SIAM J. Applied Math., 48: 1073 (1988). Methodscommonly employed to determine identity or similarity between twosequences include, but are not limited to those disclosed in Guide toHuge Computers, Martin J. Bishop, ed., Academic Press, San Diego, 1994,and Carillo, H., and Lipman, D., SIAM J. Applied Math. 48:1073 (1988).

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides of the presentinvention are immunogenic. For example, the C-TAB.G5 or C-TAB.G5.1isolated polypeptides of the present invention may have at least 50%,60%, 70%, 80%, or 90% of the immunological activity of the correspondingbacterial toxin A, and the C-TAB.G5 or C-TAB.G5.1 isolated polypeptidesmay have at least 50%, 60%, 70%, 80%, or 90% of the immunologicalactivity of the corresponding bacterial toxin B. The C-TAB.G5 orC-TAB.G5.1 isolated polypeptides of the present invention may be used asvaccines for treating, preventing, or alleviating the symptoms of CDAD.

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides of the presentinvention also include variants of the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide having SEQ ID NO: 2 or SEQ ID NO: 4, respectively. Thevariants may have amino acid insertions, substitutions and/or deletionsthat have minimal to no effect on the activity, function or shape of theisolated polypeptide. Examples of such substitutions include thesubstitution of one non-polar residue for another, the substitution ofone polar residue for another, the substitution of one basic residue foranother, or the substitution of one acidic residue for another. TheC-TAB.G5 or C-TAB.G5.1 isolated polypeptide variants may further includeinsertions, substitutions and/or deletions of amino acids in acomparison to the amino acid sequence of the extracellular domain ofnative toxin A or toxin B that yield minimal effect on the activity,function and/or structure of the polypeptide. Those skilled in the artwill recognize non-natural amino acids may also be used. Non-naturalamino acids include, for example, beta-alanine (beta-Ala), or otheromega-amino acids, such as 3-amino propionic, 2,3-diamino propionic(2,3-diaP), 4-amino butyric and so forth, alpha-aminisobutyric acid(Aib), sarcosine (Sat), ornithine (Orn), citrulline (Cit),t-butylalanine (t-BuA), t-butylglycine (t-BuG), N-methylisoleucine(N-MeIle), phenylglycine (Phg), and cyclohexylalanine (Cha), norleucine(Nle), cysteic acid (Cya) 2-naphthylalanine (2-Nal);1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic);beta-2-thienylalanine (Thi); and methionine sulfoxide (MSO).

The nucleotide sequences encoding C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptides of the present invention may be codon optimized to enhanceexpression in varying host cells. Codon optimization refers to modifyingthe nucleotide sequence in order to enhance protein expression in a hostcell of interest by replacing one or more codons of the native sequencewith codons that are more frequently used in the genes of that host cellor in the genes of the host the cell was derived from. Various speciesexhibit particular bias for certain codons of a particular amino acid.The present invention provides codon-optimized nucleotide sequenceencoding the C-TAB.G5.1 isolated polypeptide for enhanced expression inE. coli.

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides of the presentinvention may be prepared by any known techniques. For example, theisolated polypeptides may be expressed through genetic engineering. Byway of example, the translation of recombinant DNA. The C-TAB.G5 orC-TAB.G5.1 isolated polypeptides may also be prepared synthetically. Byway of example, the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides may besynthesized using the solid-phase synthetic technique initiallydescribed by Merrifield (J. Am Chem. Soc. 85:2149-2154), which isincorporated herein by reference. Other polypeptide synthesis techniquesmay be found, for example, Kent et al. (1985) in Synthetic Peptides inBiology and Medicine, eds. Alitalo et al., Elsevier Science Publishers,295-358.

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides of the presentinvention may be isolated or obtained in substantially pure form.Substantially pure means that the proteins and/or polypeptides and/orpeptides are essentially free of other substances with which they may befound in nature or in vivo systems to an extent practical andappropriate for their intended use. In particular, the C-TAB.G5 orC-TAB.G5.1 isolated polypeptides are sufficiently pure and aresufficiently free from other biological constituents of their host cellsso as to be useful in, for example, generating antibodies, sequencing,or producing pharmaceutical preparations. By techniques well known inthe art, substantially pure polypeptides may be produced in light of thenucleic acid and amino acid sequences disclosed herein. Because asubstantially purified isolated polypeptide of the invention may beadmixed with a pharmaceutically acceptable carrier in a pharmaceuticalpreparation, the isolated polypeptide may comprise only a certainpercentage by weight of the preparation. The isolated polypeptide isnonetheless substantially pure in that it has been substantiallyseparated from the substances with which it may be associated in livingsystems.

The present invention further provides isolated C-TAB.G5 or C-TAB.G5.1isolated polypeptides comprising additional polypeptides. The additionalpolypeptides may be fragments of a larger polypeptide. In oneembodiment, there are one, two, three, four, or more additionalpolypeptides fused to the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides.In some embodiments, the additional polypeptides are fused toward theamino terminus of the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides. Inother embodiments, the additional polypeptides are fused toward thecarboxyl terminus of the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides.In further embodiments, the additional polypeptides flank the C-TAB.G5or C-TAB.G5.1 isolated polypeptides. In yet further embodiments, theadditional polypeptides are dispersed between the toxin A portion andthe toxin B portion of the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides.

In some embodiments, the additional polypeptides aid in directing thesecretion or subcellular localization of the C-TAB.G5 or C-TAB.G5.1isolated polypeptides. Such polypeptides are referred to as a “signalsequence.” A secretory signal is described, for example U.S. Pat. Nos.6,291,212 and 5,547,871, both of which are herein incorporated byreference in their entirety. Secretory signal sequence encodes secretorypeptides. A secretory peptide is an amino acid sequence that acts todirect the secretion of C-TAB.G5 or C-TAB.G5.1 from a cell. Secretorypeptides are generally characterized by a core of hydrophobic aminoacids and are typically (but not exclusively) found at the amino terminiof newly synthesized proteins. The secretory peptide may be cleaved fromC-TAB.G5 or C-TAB.G5.1 isolated polypeptide during secretion. Secretorypeptides may contain processing sites that allow cleavage of the signalpeptide from the mature protein as it passes through the secretorypathway. Processing sites may be encoded within the signal peptide ormay be added to the signal peptide by, for example, in vitromutagenesis. Secretory signal sequences may be required for a complexseries of post-translational processing steps to allow for secretion ofC-TAB.G5 or C-TAB.G5.1. The signal sequence may immediately follow theinitiation codon and encodes a signal peptide at the amino-terminal endof C-TAB.G5 or C-TAB.G5.1. The signal sequence may precede the stopcodon and encodes a signal peptide at the carboxy-terminal end ofC-TAB.G5 or C-TAB.G5.1. In most cases, the signal sequence is cleavedoff by a specific protease, called a signal peptidase. Examples of asecretory signal sequences include, but are not limited to ompA, pelB,and ST pre-pro.

In some embodiments, the additional polypeptides aid the stabilization,structure and/or the purification of the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptides. In some embodiments the additional polypeptides maycomprise an epitope. In other embodiments, the additional polypeptidesmay comprise an affinity tag. By way of example, fusion of a polypeptidecomprising an epitope and/or an affinity tag to the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide may aid purification and/oridentification of the polypeptide. By way of example, the polypeptidesegment may be a His-tag, a myc-tag, an S-peptide tag, a MBP tag(maltose binding protein), a GST tag (glutathione S-transferase), a FLAGtag, a thioredoxin tag, a GFP tag (green fluorescent protein), a BCCP(biotin carboxyl carrier protein), a calmodulin tag, a Strep tag, anHSV-epitope tag, a V5-epitope tag, and a CBP tag. The use of suchepitopes and affinity tags is known to those skilled in the art.

In further embodiments, the additional polypeptides may provide aC-TAB.G5 or C-TAB.G5.1 isolated polypeptide comprising sites forcleavage of the polypeptide. As an example, a polypeptide may be cleavedby hydrolysis of the peptide bond. In some embodiments, the cleavage isperformed by an enzyme. In some embodiments, cleavage occurs in thecell. In other embodiments, cleavage occurs through artificialmanipulation and/or artificial introduction of a cleaving enzyme. By wayof example, cleavage enzymes may include pepsin, trypsin, chymotrypsin,thrombin, and/or Factor Xa. Cleavage allows ease of isolating theC-TAB.G5 or C-TAB.G5.1 isolated polypeptides from the polypeptides.Cleavage may further allow for the separation of the toxin A portionfrom the toxin B portion. Cleavage may also allow isolation of theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide fused to polypeptides fromother polypeptides, such as through cleavage of an epitope utilized topurify the expressed protein.

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides may further possessadditional structural modifications not shared with the same organicallysynthesized peptide, such as adenylation, carboxylation, glycosylation,hydroxylation, methylation, phosphorylation or myristylation. Theseadded structural modifications may be further be selected or preferredby the appropriate choice of recombinant expression system. On the otherhand, fusion polypeptides may have its sequence extended by theprinciples and practice of organic synthesis.

The present invention also provides nucleic acids encoding the C-TAB.G5or C-TAB.G5.1 isolated polypeptides comprising a polypeptide portionobtained from C. difficile toxin A and a polypeptide portion obtainedfrom C. difficile toxin B. Nucleic acids may include single or doublestranded forms of deoxyribonucleotides or ribonucleotides or polymersthereof. The present invention provides ribonucleic acids encoding theC-TAB.G5 or C-TAB.G5.1 isolated polypeptides. The present invention alsoprovides for nucleic acids that hybridize under stringent conditions toa nucleic acid encoding the C-TAB.G5 or C-TAB.G5.1 isolated polypeptideand the complement thereof. Stringent conditions refer to the degree ofhomology between a probe and a filter-bound nucleic acid; the higher thestringency, the higher percent homology between the probe and filterbound nucleic acid. The temperature for a stringent wash may bedetermined based on the Tm of the nucleic acid (based on G/C content).Stringent conditions may further be affected by the concentration ofsalt in a buffer, such as standard sodium citrate (SSC). The presentinvention provides for nucleic acids having about 85%, 86%, 87%, 88%,89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequencesimilarity or sequence identity with SEQ ID NO: 1.

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptide may further comprise alinker region, for instance a linker less than about 50, 40, 30, 20, 10,9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid residues. The linker can becovalently linked to and between the polypeptide portion derived fromtoxin A or portion thereof and the polypeptide portion derived fromtoxin B.

The present invention provides nucleic acids encoding the C-TAB.G5 orC-TAB.G5.1 isolated polypeptides that are degenerate to SEQ ID NO: 1 orSEQ ID NO: 3, respectively. The degeneracy of the genetic code permitsvariations of the nucleotide sequence of a toxin A protein, a toxin Bprotein and/or isolated polypeptide of interest, while still producing apolypeptide having the identical amino acid sequence as the polypeptideencoded by the native DNA sequence. The procedure, known as “codonoptimization” (described in U.S. Pat. No. 5,547,871 which isincorporated herein by reference in its entirety) provides one with ameans of designing such an altered DNA sequence. The design of codonoptimized genes should take into account a variety of factors, includingthe frequency of codon usage in an organism, nearest neighborfrequencies, RNA stability, the potential for secondary structureformation, the route of synthesis and the intended future DNAmanipulations of that gene. In particular, available methods may be usedto alter the codons encoding a given isolated polypeptide with thosemost readily recognized by yeast when yeast expression systems are used,or by insect cells when the insect cell expression system is used. Thedegeneracy of the genetic code also permits the same amino acid sequenceto be encoded and translated in many different ways. For example,leucine, serine and arginine are each encoded by six different codons,while valine, proline, threonine, alanine and glycine are each encodedby four different codons. However, the frequency of use of suchsynonymous codons varies from genome to genome among eukaryotes andprokaryotes. For example, synonymous codon-choice patterns among mammalsare very similar, while evolutionarily distant organisms such as yeast(such as S. cerevisiae), bacteria (such as E. coli) and insects (such asD. melanogaster) reveal a clearly different pattern of genomic codon usefrequencies (Grantham, R., et al., Nucl. Acid Res., 8, 49-62 (1980);Grantham, R., et al., Nucl. Acid Res., 9, 43-74 (1981); Maroyama, T., etal., Nucl. Acid Res., 14, 151-197 (1986); Aota, S., et al., Nucl. AcidRes., 16, 315-402 (1988); Wada, K., et al., Nucl. Acid Res., 19 Supp.,1981-1985 (1991); Kurland, C. G., FEBS Lett., 285, 165-169 (1991)).These differences in codon-choice patterns appear to contribute to theoverall expression levels of individual genes by modulating peptideelongation rates. (Kurland, C. G., FEBS Lett., 285, 165-169 (1991);Pedersen, S., EMBO J., 3, 2895-2898 (1984); Sorensen, M. A., J. Mol.Biol., 207, 365-377 (1989); Randall, L. L., et al., Eur. J. Biochem.,107, 375-379 (1980); Curran, J. F., and Yarus, M., J. Mol. Biol., 209,65-77 (1989); Varenne, S., et al., J. Mol. Biol., 180, 549-576 (1984),Varenne, S., et al., J. Mol, Biol., 180, 549-576 (1984); Garel, J.-P.,J. Theor. Biol., 43, 211-225 (1974); Ikemura, T., J. Mol. Biol., 146,1-21 (1981); Ikemura, T., J. Mol. Biol., 151, 389-409 (1981)).

The preferred codon usage frequencies for a synthetic gene shouldreflect the codon usages of nuclear genes derived from the exact (or asclosely related as possible) genome of the cell/organism that isintended to be used for recombinant protein expression.

Preferred methods to determine identity are designed to give the largestmatch between the two sequences tested. Methods to determine identityand similarity are codified in computer programs. Preferred computerprogram methods to determine identity and similarity between twosequences include, but are not limited to, GCG program package(Devereux, et al., Nucl. Acid Res. 12(1):387 (1984)), BLASTP, BLASTN,FASTA (Atschul, et al., J. Mol. Biol. 215:403 (1990)). The degree ofsimilarity or identity referred to above is determined as the degree ofidentity between the two sequences, often indicating a derivation of thefirst sequence from the second. The degree of identity between twonucleic acids may be determined by means of computer programs known inthe art such as GAP provided in the GCG program package (Needleman andWunsch J. Mol. Biol. 48:443-453 (1970)). For purposes of determining thedegree of identity between two nucleic acids for the present invention,GAP is used with the following settings: GAP creation penalty of 5.0 andGAP extension penalty of 0.3.

The present invention also provides a vector comprising a nucleic acidencoding for the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide. A vectormay be any of a number of nucleic acids into which a desired sequencemay be inserted by restriction and ligation for transport betweendifferent genetic environments or for expression in a host cell. Vectorsare typically composed of DNA, although RNA vectors are also available.Vectors include, but are not limited to, plasmids and phagemids. Acloning vector is one which is able to replicate in a host cell, andwhich is further characterized by one or more endonuclease restrictionsites at which the vector may be cut in a determinable fashion and intowhich a desired DNA sequence may be ligated such that the newrecombinant vector retains its ability to replicate in the host cell. Inthe case of plasmids, replication of the desired sequence may occur manytimes as the plasmid increases in copy number within the host bacteriumor just a single time per host before the host reproduces by mitosis. Inthe case of phage, replication may occur actively during a lytic phaseor passively during a lysogenic phase.

Vectors may further contain a promoter sequence. A promoter may includean untranslated nucleic acid usually located upstream of the codingregion that contains the site for initiating transcription of thenucleic acid. The promoter region may also include other elements thatact as regulators of gene expression. In further embodiments of theinvention, the expression vector contains an additional region to aid inselection of cells that have the expression vector incorporated. Thepromoter sequence is often bounded (inclusively) at its 3′ terminus bythe transcription initiation site and extends upstream (5′ direction) toinclude the minimum number of bases or elements necessary to initiatetranscription at levels detectable above background. Within the promotersequence will be found a transcription initiation site, as well asprotein binding domains responsible for the binding of RNA polymerase.Eukaryotic promoters will often, but not always, contain “TATA” boxesand “CAT” boxes.

Vectors may further contain one or more marker sequences suitable foruse in the identification and selection of cells which have beentransformed or transfected with the vector. Markers include, forexample, genes encoding proteins which increase or decrease eitherresistance or sensitivity to antibiotics or other compounds, genes whichencode enzymes whose activities are detectable by standard assays knownin the art (e.g., 0-galactosidase or alkaline phosphatase), and geneswhich visibly affect the phenotype of transformed or transfected cells,hosts, colonies or plaques. Preferred vectors are those capable ofautonomous replication and expression of the structural gene productspresent in the DNA segments to which they are operably joined.

An expression vector is one into which a desired nucleic acid may beinserted by restriction and ligation such that it is operably joined toregulatory sequences and may be expressed as an RNA transcript.Expression refers to the transcription and/or translation of anendogenous gene, transgene or coding region in a cell.

A coding sequence and regulatory sequences are operably joined when theyare covalently linked in such a way as to place the expression ortranscription of the coding sequence under the influence or control ofthe regulatory sequences. If it is desired that the coding sequences betranslated into a functional protein, two DNA sequences are said to beoperably joined if induction of a promoter in the 5′ regulatorysequences results in the transcription of the coding sequence and if thenature of the linkage between the two DNA sequences does not (1) resultin the introduction of a frame-shift mutation, (2) interfere with theability of the promoter region to direct the transcription of the codingsequences, or (3) interfere with the ability of the corresponding RNAtranscript to be translated into a protein. Thus, a promoter regionwould be operably joined to a coding sequence if the promoter regionwere capable of effecting transcription of that DNA sequence such thatthe resulting transcript might be translated into the desired protein orpolypeptide.

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptides of the presentinvention may be produced by expressing the encoding nucleic acid inhost cells. The nucleic acid may be transformed or transfected into hostcells. Accordingly, some aspects of the present invention include thetransformation and/or transfection of nucleic acid encoding the C-TAB.G5or C-TAB.G5.1 isolated polypeptides. Transformation is the introductionof exogenous or heterologous nucleic acid to the interior of aprokaryotic cell. Transfection is the introduction of exogenous orheterologous nucleic acid to the interior of a eukaryotic cell. Thetransforming or transfecting nucleic acid may or may not be integrated(covalently linked) into chromosomal DNA making up the genome of thecell. In prokaryotes, for example, the transforming nucleic acid may bemaintained on an episomal element such as a plasmid or viral vector.With respect to eukaryotic cells, a stably transfected cell is one inwhich the transfecting nucleic acid has become integrated into achromosome so that it is inherited by daughter cells through chromosomereplication. This stability is demonstrated by the ability of theeukaryotic cell to establish cell lines or clones comprised of apopulation of daughter cells containing the transfected nucleic acid.

Higher eukaryotic cell cultures may be used to express the proteins ofthe present invention, whether from vertebrate or invertebrate cells,including insects, and the procedures of propagation thereof are known(see, for example, Kruse et al. (1973) Tissue Culture, Academic Press).

Host cells and vectors for replicating the nucleic acids and forexpressing the encoded C-TAB.G5 or C-TAB.G5.1 isolated polypeptides arealso provided. Any vectors or host cells may be used, whetherprokaryotic or eukaryotic. Many vectors and host cells are known in theart for such purposes. It is well within the skill of the art to selectan appropriate set for the desired application.

DNA sequences encoding toxin A and toxin B, or portions thereof may becloned from a variety of genomic or cDNA libraries derived from C.difficile and other known toxin A and toxin B expressing prokaryotesknown in the art. The techniques for isolating such DNA sequences usingprobe-based methods are conventional techniques and are well known tothose skilled in the art. Probes for isolating such DNA sequences may bebased on published DNA or protein sequences. Alternatively, thepolymerase chain reaction (PCR) method disclosed by Mullis et al. (U.S.Pat. No. 4,683,195) and Mullis (U.S. Pat. No. 4,683,202), incorporatedherein by reference may be used. The choice of library and selection ofprobes for the isolation of such DNA sequences is within the level ofordinary skill in the art.

Suitable host cells may be derived from prokaryotes or eukaryotes.Suitable prokaryote hosts include: Pseudomonas such as P. aeruginosa,Escherichia coli, Staphylococcus such as S. aureus and S. epidermidis,Serratia marcescens, Bacillus such as B. subtillis and B. megaterium,Clostridium sporogenes, Enterococcus faecalis, Micrococcus such as M.luteus and M. roseus, and Proteus vulgaris. Suitable host cells forexpressing the polypeptides of the present invention in highereukaryotes include: yeasts such as Saccharomyces (e.g. S. cerevisiae);293 (human embryonic kidney) (ATCC CRL-1573); 293F (Invitrogen, CarlsbadCalif.); 293T and variant 293T/17 (293tsA1609neo and variant ATCCCRL-11268) (human embryonic kidney transformed by SV40 T antigen); COS-7(monkey kidney CVI line transformed by SV40)(ATCC CRL1651); BHK (babyhamster kidney cells) (ATCC CRL10); CHO (Chinese hamster ovary cells);mouse Sertoli cells; CVI (monkey kidney cells) (ATCC CCL70); VERO76(African green monkey kidney cells) (ATCC CRL1587); HeLa (human cervicalcarcinoma cells) (ATCC CCL2); MDCK (canine kidney cells) (ATCC CCL34);BRL3A (buffalo rat liver cells) (ATCC CRL1442); W138 (human lung cells)(ATCC CCL75); HepG2 (human liver cells) (HB8065); and MMT 060652 (mousemammary tumor) (ATCC CCL51).

In other embodiments, the present invention provides nucleic acidsencoding an isolated polypeptide comprising the C-TAB.G5 or C-TAB.G5.1isolated polypeptides and additional polypeptides. Vectors useful forconstructing eukaryotic expression systems for the production of fusionpolypeptides comprise nucleic acid encoding the isolated polypeptideoperatively linked to an appropriate transcriptional activationsequence, such as a promoter and/or operator. Other typical features mayinclude appropriate ribosome binding sites, termination codons,enhancers, terminators, or replicon elements. These additional featurescan be inserted into the vector at the appropriate site or sites byconventional splicing techniques such as restriction endonucleasedigestion and ligation.

In some embodiments, additional nucleic acids may be fused to thenucleic acid encoding the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides.The fused nucleic acid may encode polypeptides that may aid inpurification and/or immunogenicity and/or stability without shifting thecodon reading frame of the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide.The fused nucleic acids may encode a secretory sequence, that may or maynot be cleaved from the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides.The fused nucleic acids may not elongate the expressed polypeptidesignificantly. The fused nucleic acids may encode for less than sixtyextra amino acids to the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides.In some embodiments, the fused nucleic acids follow after the nucleicacid encoding the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides. In otherembodiments, the fused nucleic acids precede the nucleic acid encodingthe C-TAB.G5 or C-TAB.G5.1 isolated polypeptides. In other embodiments,the fused nucleic acids flank the nucleic acid encoding the C-TAB.G5 orC-TAB.G5.1 isolated polypeptides.

In some embodiments, the fused nucleic acids may encode for apolypeptide to aid purification of the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptides. In some embodiments the fused nucleic acid will encode foran epitope and/or an affinity tag. Examples of polypeptides that aidpurification include, but are not limited to, a His-tag, a myc-tag, anS-peptide tag, a MBP tag, a GST tag, a FLAG tag, a thioredoxin tag, aGFP tag, a BCCP, a calmodulin tag, a Strep tag, an HSV-epitope tag, aV5-epitope tag, and a CBP tag. In other embodiments, the fused nucleicacid may encode for a C-TAB.G5 or C-TAB.G5.1 isolated polypeptide thathas a site directed for, or prone to, cleavage. In one embodiment, thefused nucleic acid may encode for polypeptides comprising sites ofenzymatic cleavage. In further embodiments, the enzymatic cleavage mayaid in isolating the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides, aswell as other fused polypeptide segments, from yet other polypeptides.By way of example, an intermediary nucleic acid that encodes for anenzymatic cleavage site placed between nucleic acids that encode forC-TAB.G5 or C-TAB.G5.1 isolated polypeptide and an epitope may allow forlater separation of the expressed C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptides and the epitope. Such sites may also be present between thetoxin A portion and the toxin B portion.

The present invention also provides for expression systems designed toassist in expressing and providing the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptides. The expression system may comprise a host cell transformedor transfected with a nucleic acid encoding the C-TAB.G5 or C-TAB.G5.1isolated polypeptide. The host cell may be a prokaryote. The prokaryotemay be E. coli. The host cell may be an eukaryotic cell.

The expression system may further comprise agents to aid in selection ofhost cells successfully transformed or transfected with a nucleic acidencoding the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides. For example,the nucleic acid encoding the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide may further express a gene to assist the host cell inresistance to antibiotics, such as genes to resist kanamycin orgentamycin or ampicillin or penicillin. Such resistant genes will allowfor selection of host cells that have properly incorporated the nucleicacid encoding the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide, as isknown to those skilled in the art.

Another aspect of the invention is directed to the generation ofantibodies. Examples of antibodies encompassed by the present invention,include, but are not limited to, antibodies produced by immunizing asubject with the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide. Antibodiesgenerated by immunizing with the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide may bind specifically to toxin A or toxin B, or they maycross react with the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide. Theantibodies produced by the C-TAB.G5 or C-TAB.G5.1 isolated polypeptideof the present invention may be characterized using methods well knownin the art.

The antibodies produced by using the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide of the present invention can encompass monoclonalantibodies, polyclonal antibodies, antibody fragments (e.g., Fab, Fab′,F(ab′)2, Fv, Fc, etc.), chimeric antibodies, bispecific antibodies,heavy chain only antibodies, heteroconjugate antibodies, single chain(ScFv), single domain antibodies, variants thereof, isolatedpolypeptides comprising an antibody portion, humanized antibodies, andany other modified configuration of the immunoglobulin molecule thatcomprises an antigen recognition site of the required specificity,including glycosylation variants of antibodies, amino acid sequencevariants of antibodies, and covalently modified antibodies. Preferredantibodies are derived from murine, rat, human, rabbit, canine, porcine,dromedary, camel, llama, feline, primate, or any other origin (includingchimeric, fragment and/or humanized antibodies).

In other embodiments, the antibodies produced by immunizing with theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide are then humanized bymethods known in the art. A humanized antibody is an immunoglobulinmolecule that contains minimal sequence derived from non-humanimmunoglobulin. In yet other embodiments, fully human antibodies areobtained by using commercially available mice that have been engineeredto express specific human immunoglobulin proteins. In other embodiments,the antibodies are chimeric. A chimeric antibody is an antibody thatcombines characteristics from two different antibodies. Methods ofpreparing chimeric antibodies are known in the art.

In other embodiments, the nucleotide sequence that encodes theantibodies is obtained and then cloned into a vector for expression orpropagation. In another embodiment, antibodies are made recombinantlyand expressed using methods known in the art. By way of example, theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide may be used as an antigenfor the purposes of isolating recombinant antibodies by thesetechniques. Antibodies can be made recombinantly by using the genesequence to express the antibody recombinantly in host cells. Methodsfor making variants of antibodies and recombinant antibodies are knownin the art.

In other embodiments, the antibodies are bound to a carrier byconventional methods in the art, for use in, for example, isolating orpurifying native toxin A or toxin B or detecting native toxin A or toxinB or C. difficile in a biological sample or specimen.

Compositions and Formulations

The present invention also provides compositions comprising C-TAB.G5 orC-TAB.G5.1 isolated polypeptides. The compositions may be pharmaceuticalcompositions comprising the C-TAB.G5 or C-TAB.G5.1 isolated polypeptideand a pharmaceutically acceptable carrier. The compositions used in themethods of the invention generally comprise, by way of example and notlimitation, and effective amount of the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide (e.g., an amount sufficient to induce an immune response) ofthe invention or an antibody against the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptides (e.g., an amount of a neutralizing antibody sufficient tomitigate infection, alleviate a symptom of infection and/or preventinfection). The pharmaceutical composition may further comprisepharmaceutically acceptable carriers, excipients, or stabilizers knownin the art (see generally Remington, (2005) The Science and Practice ofPharmacy, Lippincott, Williams and Wilkins).

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptide of the invention may beused for methods for immunizing or treating humans and/or animals withthe CDAD. Therefore, the C-TAB.G5 or C-TAB.G5.1 isolated polypeptidesmay be used within a pharmaceutical composition. The pharmaceuticalcomposition of the present invention may further encompasspharmaceutically acceptable carriers and/or excipients. Thepharmaceutically acceptable carriers and/or excipients useful in thisinvention are conventional and may include buffers, stabilizers,diluents, preservatives, and solubilizers. Remington's PharmaceuticalSciences, by E. W. Martin, Mack Publishing Co., Easton, Pa., 15thEdition (1975), describes compositions and formulations suitable forpharmaceutical delivery of the polypeptides herein disclosed. Ingeneral, the nature of the carrier or excipients will depend on theparticular mode of administration being employed. For instance,parenteral formulations usually comprise injectable fluids that includepharmaceutically and physiologically acceptable fluids such as water,physiological saline, balanced salt solutions, aqueous dextrose,glycerol or the like as a vehicle. For solid compositions (e. g. powder,pill, tablet, or capsule forms), conventional non-toxic solid carrierscan include, for example, pharmaceutical grades of mannitol, lactose,starch, or magnesium stearate. In addition to biologically neutralcarriers, pharmaceutical compositions to be administered can containminor amounts of non-toxic auxiliary substances, such as wetting oremulsifying agents, preservatives, and pH buffering agents and the like,for example sodium acetate or sorbitan monolaurate.

In one embodiment the pharmaceutical composition may further comprise animmunostimulatory substance, such as an adjuvant. The adjuvant can beselected based on the method of administration and may include mineraloil-based adjuvants such as Freund's complete and incomplete adjuvant,Montanide incomplete Seppic adjuvant such as ISA, oil in water emulsionadjuvants such as the Ribi adjuvant system, syntax adjuvant formulationcontaining muramyl dipeptide, aluminum hydroxide or aluminum saltadjuvant (alum), polycationic polymer, especially polycationic peptide,especially polyarginine or a peptide containing at least two LysLeuLysmotifs, especially KLKLLLLLKLK (SEQ ID NO: 21), immunostimulatoryoligodeoxynucleotide (ODN) containing non-methylated cytosine-guaninedinucleotides (CpG) in a defined base context (e.g. as described in WO96/02555) or ODNs based on inosine and cytidine (e.g. as described in WO01/93903), or deoxynucleic acid containing deoxy-inosine and/ordeoxyuridine residues (as described in WO 01/93905 and WO 02/095027),especially Oligo(dIdC)₁₃ (as described in WO 01/93903 and WO 01/93905),neuroactive compound, especially human growth hormone (described in WO01/24822), or combinations thereof. Such combinations are according tothe ones e.g. described in WO 01/93905, WO 02/32451, WO 01/54720, WO01/93903, WO 02/13857, WO 02/095027 and WO 03/047602. Preferably, theadjuvant is aluminum hydroxide adjuvant.

Acceptable carriers, excipients, or stabilizers are nontoxic torecipients at the dosages and concentrations that are administered.Carriers, excipients or stabilizers may further comprise buffers.Examples of excipients include, but are not limited to, carbohydrates(such as monosaccharide and disaccharide), sugars (such as sucrose,mannitol, and sorbitol), phosphate, citrate, antioxidants (such asascorbic acid and methionine), preservatives (such as phenol, butanol,benzanol; alkyl parabens, catechol, octadecyldimethylbenzyl ammoniumchloride, hexamethoniuni chloride, resorcinol, cyclohexanol, 3-pentanol,benzalkonium chloride, benzethonium chloride, and m-cresol), lowmolecular weight polypeptides, proteins (such as serum albumin orimmunoglobulins), hydrophilic polymers amino acids, chelating agents(such as EDTA), salt-forming counter-ions, metal complexes (such asZn-protein complexes), and non-ionic surfactants (such as TWEEN™ andpolyethylene glycol).

The pharmaceutical composition of the present invention may furthercomprise additional agents that serve to enhance and/or complement thedesired effect. By way of example, to enhance the immunogenicity theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide of the invention beingadministered as a subunit vaccine, the pharmaceutical composition mayfurther comprise an adjuvant.

An example of a pharmaceutical composition may be an immunogeniccomposition. The present invention provides immunogenic compositionscomprising the C-TAB.G5 or C-TAB.G5.1 isolated polypeptides. Theimmunogenic composition may further include a pharmaceuticallyacceptable carrier or other carriers and/or excipients in a formulationsuitable for injection in a mammal. An immunogenic composition is anycomposition of material that elicits an immune response in a mammalianhost when the immunogenic composition is injected or otherwiseintroduced. The immune response may be humoral, cellular, or both. Abooster effect refers to an increased immune response to an immunogeniccomposition upon subsequent exposure of the mammalian host to the sameimmunogenic composition. A humoral response results in the production ofantibodies by the mammalian host upon exposure to the immunogeniccomposition.

The immunogenic compositions of the present invention elicit an immuneresponse in a mammalian host, including humans and other animals. Theimmune response may be either a cellular dependent response or anantibody dependent response or both; and further the response mayprovide immunological memory or a booster effect or both in themammalian host. These immunogenic compositions are useful as vaccinesand may provide a protective response by the mammalian subject or hostto infection by strains of C. difficile.

The present invention further includes methods for producing animmunogenic composition by constructing the nucleic acid encoding theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide and expressing C-TAB.G5 orC-TAB.G5.1 isolated polypeptide component in a microbial host;recovering the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide from aculture of the host; conjugating the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide to a second protein component, and recovering the conjugatedprotein and polysaccharide component. The nucleic acid encoding theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide may be maintained throughoutthe growth of the host by constant and stable selective pressure.Maintenance of the expression vector may be conferred by incorporationin the expression vector of a genetic sequence that encodes a selectivegenotype, the expression of which in the microbial host cell results ina selective phenotype. A selective genotype sequence may also include agene complementing a conditional lethal mutation. Other geneticsequences may be incorporated in the expression vector, such as otherdrug resistance genes or genes that complement lethal mutations.Microbial hosts may include: Gram positive bacteria; Gram negativebacteria, such as E. coli; yeasts; filamentous fungi; mammalian cells;insect cells; or plant cells.

The methods of the present invention also provide for a level ofexpression of the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide in thehost at a level greater than about 50 mg/liter of the culture, a levelgreater than about 100 mg/liter, a level greater than about 500mg/liter, or a level greater than about 1 g/liter. This invention alsoprovides that the protein may be recovered by any number of methodsknown to those in the art for the isolation and recovery of proteins,such as by ammonium sulfate precipitation followed by ion exchangechromatography.

The present invention further includes methods for preparing theimmunogenic composition that provides that the protein component isconjugated to a second protein component by one of a number of meansknown to those in the art, such as an amidization reaction.

The present invention also provides formulations comprising the C-TAB.G5or C-TAB.G5.1 isolated polypeptide for treating and preventing CDAD. Inone embodiment, the formulation may include the C-TAB.G5 or C-TAB.G5.1isolated polypeptide of the present invention, an adjuvant, and apharmaceutically acceptable carrier. In another embodiment, theformulation includes the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide ofthe present invention, or consists essentially of one or more C-TAB.G5or C-TAB.G5.1 isolated polypeptides of the present invention. Theformulation may comprise the C-TAB.G5 or C-TAB.G5.1 isolated polypeptideof the present invention and an adjuvant. The formulation may furtherinclude an additional antigen or a drug. Moreover, the formulation mayinclude one or more drugs and may in addition to the isolatedpolypeptide and/or adjuvant include one or more drugs.

The formulation comprising the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide may be in liquid or dry form. A dry formulation may beeasily stored and transported. Dry formulations break the cold chainrequired from the vaccine's place of manufacture to the locale wherevaccination occurs. Alternatively, the dry, active ingredient of theformulation per se may be an improvement by providing a solidparticulate form that is taken up and processed by antigen presentingcells. These possible mechanisms are discussed not to limit the scope ofthe invention or its equivalents, but to provide insight into theoperation of the invention and to guide the use of this formulation inimmunization and vaccination.

Dry formulations of the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide maybe provided in various forms: for example, fine or granulated powders,lyophilized powder, uniform films, pellets, and tablets. It may be airdried, dried with elevated temperature, lyophilized, freeze or spraydried, coated or sprayed on a solid substrate and then dried, dusted ona solid substrate, quickly frozen and then slowly dried under vacuum, orcombinations thereof. If different molecules are active ingredients ofthe formulation, they may be mixed in solution and then dried, or mixedin dry form only.

Formulations comprising the C-TAB.G5 or C-TAB.G5.1 isolated polypeptidein liquid or solid form, such as a dry form, may be applied with one ormore adjuvants at the same or separate sites or simultaneously or infrequent, repeated applications. The formulation may include otherantigens such that administration of the formulation induces an immuneresponse to multiple antigens. In such a case, the other antigens mayhave different chemical structures so as to induce an immune responsespecific for different antigens. At least one antigen and/or adjuvantmay be maintained in dry form prior to administration. Subsequentrelease of liquid from a reservoir or entry of liquid into a reservoircontaining the dry ingredient of the formulation will at least partiallydissolve that ingredient.

Solids (e.g., particles of nanometer or micrometer dimensions) may alsobe incorporated in the formulation. Solid forms (e.g., nanoparticles ormicroparticles) may aid in dispersion or solubilization of activeingredients; provide a point of attachment for adjuvant, C-TAB.G5 orC-TAB.G5.1 isolated polypeptide, or both to a substrate that can beopsonized by antigen presenting cells, or combinations thereof.Prolonged release of the formulation from a porous solid formed as asheet, rod, or bead acts as a depot.

At least one ingredient or component of the formulation (i.e., C-TAB.G5or C-TAB.G5.1 isolated polypeptide, adjuvant, or drug) may be providedin dry form prior to administration of the formulation. This formulationmay also be used in conjunction with conventional enteral, mucosal, orparenteral immunization techniques.

The formulation comprising the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide may be manufactured under aseptic conditions acceptable toappropriate regulatory agencies (e.g., Food and Drug Administration,EMEA for biologicals and vaccines. Optionally, components such asdesiccants, excipients, stabilizers, humectants, preservatives, orcombinations thereof may be included in the formulation even though theyare immunologically inactive. They may, however, have other desirableproperties or characteristics.

Processes for manufacturing a pharmaceutical formulation are well known.The components of the formulation may be combined with apharmaceutically-acceptable carrier or vehicle, as well as anycombination of optional additives (e.g., diluents, binders, excipients,stabilizers, desiccants, preservatives, colorings). The use of solidcarriers, and the addition of excipients to assist in solubilization ofdry components or stabilizers of immunogenic or adjuvant activity, arepreferred embodiments. See, generally, Ullmann's Encyclopedia ofIndustrial Chemistry, 6^(th) Ed. (electronic edition, 2003); Remington'sPharmaceutical Sciences, 22^(nd) (Gennaro, 2005, Mack Publishing);Pharmaceutical Dosage Forms, 2^(nd) Ed. (various editors, 1989-1998,Marcel Dekker); and Pharmaceutical Dosage Forms and Drug DeliverySystems (Ansel et al., 2005, Williams & Wilkins).

Good manufacturing practices are known in the pharmaceutical industryand regulated by government agencies (e.g., Food and DrugAdministration, EMEA. Sterile liquid formulations may be prepared bydissolving an intended component of the formulation in a sufficientamount of an appropriate solvent, followed by sterilization byfiltration to remove contaminating microbes. Generally, dispersions areprepared by incorporating the various sterilized components of theformulation into a sterile vehicle which contains the basic dispersionmedium. For production of solid forms that are required to be sterile,vacuum drying or freeze drying can be used.

In general, solid dosage forms (e.g., powders, granules, pellets,tablets) can be made from at least one active ingredient or component ofthe formulation.

Suitable tableting procedures are known. The formulation may also beproduced by encapsulating solid forms of at least one active ingredient,or keeping them separate from liquids in compartments or chambers. Thesize of each dose and the interval of dosing to the subject may be usedto determine a suitable size and shape of the tablet, capsule,compartment, or chamber.

Formulations will contain an effective amount of the active ingredients(e.g., drug, antigen and adjuvant) together with carrier or suitableamounts of vehicle in order to provide pharmaceutically-acceptablecompositions suitable for administration to a human or animal.

The relative amounts of active ingredients, such as amounts of theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide, within a dose and thedosing schedule may be adjusted appropriately for efficaciousadministration to a subject (e.g., animal or human). This adjustment mayalso depend on the subject's particular disease or condition, andwhether treatment or prophylaxis is intended. To simplify administrationof the formulation to the subject, each unit dose contains the activeingredients in predetermined amounts for a single round of immunization.

There are numerous causes of polypeptide instability or degradation,including hydrolysis and denaturation. In the case of denaturation, theconformation or three-dimensional structure of the protein is disturbedand the protein unfolds from its usual globular structure. Rather thanrefolding to its natural conformation, hydrophobic interaction may causeclumping of molecules together (i.e., aggregation) or refolding to anunnatural conformation. Either of these results may entail diminution orloss of immunogenic or adjuvant activity. Stabilizers may be added tolessen or prevent such problems.

The formulation, or any intermediate in its production, may bepretreated with protective agents (i.e., cryoprotectants and drystabilizers) and then subjected to cooling rates and final temperaturesthat minimize ice crystal formation. By proper selection ofcryoprotective agents and use of pre-selected drying parameters, almostany formulation might be cryoprepared for a suitable desired end use.

It should be understood in the following discussion of optionaladditives like excipients, stabilizers, desiccants, and preservativesare described by their function. Thus, a particular chemical may act assome combination of recipient, stabilizer, desiccant, and/orpreservative. Such chemical would be immunologically-inactive because itdoes not directly induce an immune response, but it increases theresponse by enhancing immunological activity of the antigen or adjuvant:for example, by reducing modification of the antigen or adjuvant, ordenaturation during drying and dissolving cycles.

Stabilizers include cyclodextrin and variants thereof (see U.S. Pat. No.5,730,969). Suitable preservatives such as sucrose, mannitol, sorbitol,trehalose, dextran, and glycerin can also be added to stabilize thefinal formulation (Howell and Miller, 1983). A stabilizer selected fromnonionic surfactants, D-glucose, D-galactose, D-xylose, D-glucuronicacid, salts of D-glucuronic acid, trehalose, dextrans, hydroxyethylstarches, and mixtures thereof may be added to the formulation. Additionof an alkali metal salt or magnesium chloride may stabilize the C-TAB.G5or C-TAB.G5.1 isolated polypeptide, optionally including serum albuminand freeze-drying to further enhance stability. The C-TAB.G5 orC-TAB.G5.1 isolated polypeptide may also be stabilized by contacting itwith a saccharide selected from the group consisting of dextran,chondroitin sulfuric acid, starch, glycogen, insulin, dextrin, andalginic acid salt. Other sugars that can be added includemonosaccharides, disaccharides, sugar alcohols, and mixtures thereof(e.g., glucose, mannose, galactose, fructose, sucrose, maltose, lactose,mannitol, xylitol). Polyols may stabilize a polypeptide, and arewater-miscible or water-soluble. Suitable polyols may be polyhydroxyalcohols, monosaccharides and disaccharides including mannitol,glycerol, ethylene glycol, propylene glycol, trimethyl glycol, vinylpyrrolidone, glucose, fructose, arabinose, mannose, maltose, sucrose,and polymers thereof. Various excipients may also stabilizepolypeptides, including serum albumin, amino acids, heparin, fatty acidsand phospholipids, surfactants, metals, polyols, reducing agents, metalchelating agents, polyvinyl pyrrolidone, hydrolyzed gelatin, andammonium sulfate.

As an example, the C-TAB.G5 or C-TAB.G5.1 isolated polypeptideformulation can be stabilized in sucrose, trehalose, poly(lactic acid)(PLA) and poly(lactide-co-glycolide) (PLGA) microspheres by suitablechoice of excipient or stabilizer (Sanchez et al., 1999). Sucrose, ortrehalose may be advantageously used as an additive because it is anon-reducing saccharide, and therefore does not cause aminocarbonylreactions with substances bearing amino groups such as proteins. Sucroseor trehalose may be combined with other stabilizers such as saccharides.

Additionally, the formulation comprising the C-TAB.G5 or C-TAB.G5.1isolated polypeptide may include therapeutic agents, such as e.g.anesthetics, analgesics, anti-inflammatories, steroids, antibiotics,antiarthritics, anorectics, antihistamines, and antineoplastics.Examples of such therapeutic agents include lidocaine and nonsteroidalanti-inflammatory drugs (NSAID). In another embodiment, the therapeuticagents are antigens and adjuvants. In still another embodiment, theformulation comprising antigen and/or adjuvant may be applied separatelybut along with other therapeutic agents, such e.g anesthetics,analgesics, anti-inflammatories, steroids, antibiotics, antiarthritics,anorectics, antihistamines, and antineoplastics. In a preferredembodiment, the antibiotics are fidaxomicin, metronidazole orvancomycin.

The formulation comprising the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide may be delivered via various routes of administration suchas e.g. intramuscularly.

Polymers may be added to the formulation and may act as an excipient,stabilizer, and/or preservative of an active ingredient as well asreducing the concentration of the active ingredient that saturates asolution used to dissolve the dry form of the active ingredient. Suchreduction occurs because the polymer reduces the effective volume of thesolution by filling the “empty” space. Thus, quantities ofantigen/adjuvant can be conserved without reducing the amount ofsaturated solution. An important thermodynamic consideration is that anactive ingredient in the saturated solution will be “driven” intoregions of lower concentration. In solution, polymers can also stabilizeand/or preserve the antigen/adjuvant-activity of solubilized ingredientsof the formulation. Such polymers include ethylene or propylene glycol,vinyl pyrrolidone, and 0-cyclodextrin polymers and copolymers.

A single or unit dose of the formulation comprising the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide suitable for administration is provided.The amount of adjuvant and/or C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide in the unit dose may be anywhere in a broad range from about0.001 μg to about 10 mg. This range may be from about 0.1 ug to about 1mg; a narrower range is from about 5 μg to about 500 μg. Other suitableranges are between about 20 μg to about 200 μg, such as e.g. about 20μg, about 75 μg or about 200 μg. A preferred dose for a C-TAB.G5 orC-TAB.G5.1 isolated polypeptide is from about 20 μg or 200 μg or less.The ratio between C-TAB.G5 or C-TAB.G5.1 isolated polypeptide andadjuvant may be about 1:1 or about 1:1.25, but higher ratios may also beused (e.g., about 1:10 or less), or lower ratios of C-TAB isolatedpolypeptide to adjuvant may also be used (e.g., about 10:1 or more).

The C-TAB.G5 or C-TAB.G5.1 isolated polypeptide may be used as anantigen and may be presented to immune cells, and an antigen-specificimmune response is induced. This may occur before, during, or afterinfection by a pathogen, such as C. difficile. Only C-TAB.G5 orC-TAB.G5.1 isolated polypeptide may be required, but no additionaladjuvant, if the immunogenicity of the formulation is sufficient to notrequire adjuvant activity. The formulation may include an additionalantigen such that application of the formulation induces an immuneresponse against multiple antigens (i.e., multivalent). Antigen-specificlymphocytes may participate in the immune response and, in the case ofparticipation by B lymphocytes, antigen-specific antibodies may be partof the immune response. The formulations described above may includedesiccants, excipients, humectants, stabilizers, and preservatives knownin the art.

The formulation comprising the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide of the present invention may be used to treat a subject(e.g., a human or animal in need of treatment such as prevention ofdisease, protection from effects of infection, reducing or alleviatingthe symptoms of a disease, such as CDAD, or combinations thereof). E.g.the formulation comprising the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide of the present invention may be used to treat a subject atrisk of CDAD, such as e.g. a subject with the following profile: i) asubject with a weaker immune system such as e.g. an elderly subject(e.g. a subject above 65 years of age) or a subject below 2 years ofage; ii) an immunocompromised subject such as e.g. a subject with AIDS;iii) a subject taking or planning to take immunosuppressing drugs; iv) asubject with planned hospitalization or a subject that is in hospital;v) a subject in or expected to go to an intensive care unit (ICU); vi) asubject that is undergoing or is planning to undergo gastrointestinalsurgery; vii) a subject that is in or planning to go to a long-term caresuch as a nursing home; viii) a subject with co-morbidities requiringfrequent and/or prolonged antibiotic use; ix) a subject that is asubject with two or more of the above mentioned profiles, such as e.g.an elderly subject that is planning to undergo a gastrointestinalsurgery; x) a subject with inflammatory bowel disease; and/or xi) asubject with recurrent CDAD such as e.g. a subject having experiencedone or more episodes of CDAD.

The treatment may vaccinate the subject against infection by thepathogen or against its pathogenic effects such as those caused by toxinsecretion. The formulation may be used therapeutically to treat existingdisease, protectively to prevent disease, to reduce the severity and/orduration of disease, to ameliorate symptoms of disease, or combinationsthereof.

The formulations comprising C-TAB.G5 or C-TAB.G5.1 isolated polypeptidesmay be delivered by various routes of administration including but notlimited to oral, subcutaneous, intradermal, intravenous, intra-arterial,intramuscular, intracardial, intraspinal, intrathoracical,intraperitoneal, intraventricular, and/or sublingual routes.

The formulation may also comprise one or more adjuvants or combinationsof adjuvants. Usually, the adjuvant and the formulation are mixed priorto presentation of the antigen but, alternatively, they may beseparately presented within a short interval of time.

Adjuvants include, for example, an oil emulsion (e.g., complete orincomplete Freund's adjuvant), Montanide incomplete Seppic adjuvant suchas ISA, oil in water emulsion adjuvants such as the Ribi adjuvantsystem, syntax adjuvant formulation containing muramyl dipeptide,aluminum hydroxide or salt adjuvant (ALUM), polycationic polymer,especially polycationic peptide, especially polyarginine or a peptidecontaining at least two LysLeuLys motifs, especially KLKLLLLLKLK (SEQ IDNO: 21), immunostimulatory oligodeoxynucleotide (ODN) containingnon-methylated cytosine-guanine dinucleotides (CpG) in a defined basecontext (e.g. as described in WO 96/02555) or ODNs based on inosine andcytidine (e.g. as described in WO 01/93903), or deoxynucleic acidcontaining deoxy-inosine and/or deoxyuridine residues (as described inWO 01/93905 and WO 02/095027), especially Oligo(dIdC)₁₃ (as described inWO 01/93903 and WO 01/93905), neuroactive compound, especially humangrowth hormone (described in WO 01/24822), or combinations thereof, achemokine (e.g., defensins 1 or 2, RANTES, MIP1-α, MIP-2, interleukin-8,or a cytokine (e.g., interleukin-1β, -2, -6, -10 or -12; interferon-γ;tumor necrosis factor-α; or granulocyte-monocyte-colony stimulatingfactor) (reviewed in Nohria and Rubin, 1994), a muramyl dipeptidevariant (e.g., murabutide, threonyl-MDP or muramyl tripeptide),synthetic variants of MDP, a heat shock protein or a variant, a variantof Leishmania major LeIF (Skeiky et al., 1995), non-toxic variants ofbacterial ADP-ribosylating exotoxins (bAREs) including variants at thetrypsin cleavage site (Dickenson and Clements, 1995) and/or affectingADP-ribosylation (Douce et al., 1997), or chemically detoxified bAREs(toxoids), QS21, Quill A,N-acetylmuramyl-L-alanyl-D-isoglutamyl-L-alanine-2-[1,2-dipalmitoyl-s-glycero-3-(hydroxyphosphoryloxy)]ethylamide(MTP-PE) and compositions containing a metabolizable oil and anemulsifying agent, wherein the oil and emulsifying agent are present inthe form of an oil-in-water emulsion having oil droplets substantiallyall of which are less than one micron in diameter (see, for example, EP0399843). Also, see Richards et al. (1995) for other adjuvants useful inimmunization.

An adjuvant may be chosen to preferentially induce antibody or cellulareffectors, specific antibody isotypes (e.g., IgM, IgD, IgA1, IgA2,secretory IgA, IgE, IgG1, IgG2, IgG3, and/or IgG4), or specific T-cellsubsets (e.g., CTL, Th1, Th2 and/or T_(DTH)) (see, for example, Munoz etal., 1990; Glenn et al., 1995).

Unmethylated CpG dinucleotides or motifs are known to activate B cellsand macrophages (Stacey et al., 1996). Other forms of DNA can be used asadjuvants. Bacterial DNAs are among a class of structures which havepatterns allowing the immune system to recognize their pathogenicorigins to stimulate the innate immune response leading to adaptiveimmune responses (Medzhitov and Janeway, 1997, Curr. Opin. Immunol.9(1): 4-9). These structures are called pathogen-associated molecularpatterns (PAMPs) and include lipopolysaccharides, teichoic acids,unmethylated CpG motifs, double-stranded RNA, and mannins. PAMPs induceendogenous signals that can mediate the inflammatory response, act asco-stimulators of T-cell function and control the effector function. Theability of PAMPs to induce these responses play a role in theirpotential as adjuvants and their targets are APCs such as macrophagesand dendritic cells. PAMPs could also be used in conjunction with otheradjuvants to induce different co-stimulatory molecules and controldifferent effector functions to guide the immune response, for examplefrom a Th2 to a Th1 response.

Other aspects of the invention is directed toward use of the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide as vaccinating agent. The vaccines orimmunogenic compositions of the present invention may employ aneffective amount of the antigen. There will be included an amount ofantigen which will cause the subject to produce a specific andsufficient immunological response so as to impart protection to thesubject from subsequent exposure to C. difficile. The antigen may be theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide. In one embodiment, theC-TAB.G5 or C-TAB.G5.1 isolated polypeptide is administered by itself orin combination with an adjuvant.

Another aspect of the invention includes use of the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide as a subunit vaccine. A subunit vaccinerefers to the use of a fragment of a pathogen as an inoculating agent.Those skilled in the art will know subunit vaccines offer a means togenerate antibodies to a particular part or region of a pathogen.

Dosage schedule of administration and efficacy of the vaccine can bedetermined by methods known in the art. The amount of the vaccine andthe immunization regimen may depend on the particular antigen and theadjuvant employed, the mode and frequency of administration, and thedesired effect (e.g., protection and/or treatment). In general, thevaccine of the invention may be administered in amounts ranging between1 μg and 100 mg, such as e.g. between 60 μg and 600 μg. A single dose ofthe vaccine comprising the C-TAB.G5 or C-TAB.G5.1 isolated polypeptidemay be in a range from about 1 μg to about 1 mg, preferably from about 5μg to about 500 μg, more preferably from about 20 μg to about 200 μg.The ratio between C-TAB.G5 or C-TAB.G5.1 isolated polypeptide andadjuvant such as alum may be about 1:1 such as e.g. 1:1.25, but higherratios may also be used (e.g., about 1:10 or less), or lower ratios mayalso be used (e.g., about 10:1 or more). In an embodiment, in thevaccine comprising the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide theadjuvant aluminum hydroxide will be used in a range from about 50 μg/mLto about 200 μg/mL, preferably in the amount about 125 μg/mL of thefinal formulation.

The vaccine comprising the C-TAB.G5 or C-TAB.G5.1 isolated polypeptidecan be administered orally, intravenously, subcutaneously,intra-arterially, intramuscularly, intracardially, intraspinally,intrathoracically, intraperitoneally, intraventricularly, and/orsublingually.

The immunization regimen can be determined by methods known in the art.Administration of the vaccine can be repeated as is determined to benecessary by one skilled in the art. For example, a priming dose may befollowed by 1, 2, 3 or more booster doses at weekly, bi-weekly ormonthly intervals. In an embodiment of the present invention, thepriming dose is followed by one or two booster administration inintervals from about 7 to about 14 days such as e.g. after 7 days and 21days after first prime. In a preferred embodiment, the therapeuticallyeffective amount of the vaccine is administered two or three times inintervals of 14 days+/−1, 2 or 3 days (bi-weekly) to a subject. In anembodiment of the present invention, the therapeutically effectiveamount of the vaccine is administered once.

Still another aspect is directed to the population which can be treatedaccording to the present invention. In one embodiment, the populationincludes healthy individuals who are at risk of exposure to C.difficile, especially, the individuals impending hospitalization orresidence in a care facility, as well as personals in hospitals, nursinghomes and other care facilities. In another embodiment, the populationincludes previously infected patients who relapsed after discontinuationof antibiotic treatment, or patients for whom antibiotic treatment isnot efficient.

In one more embodiment of the invention, the population includesindividuals who are at least 18 years or more of age. In one preferredembodiment, the human subject is from 18 to 65 years old. In anotherpreferred embodiment, the human subject is elderly individuals over 65years of age. The latter age group being the most vulnerable populationsuffering from C. difficile infections. In some more embodiment, thehuman subject is younger than 18 years of age.

Methods of Using the C-TAB.G5 or C-TAB.G5.1 Isolated Polypeptide

The present invention also provides methods of using the isolatedpolypeptide. For example, the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide may be used to prevent or treat diseases associated with C.difficile. By way of example, introducing the isolated polypeptides ofthe present invention into the immune system of a subject may induce animmune response that includes the subject producing antibodies directedagainst the isolated polypeptide. Such antibodies are useful forrecognizing C. difficile.

The present invention provides methods of delivering isolatedpolypeptides to a subject comprising administering the isolatedpolypeptide to a subject. The isolated polypeptide may be administeredas a liquid or as a solid. The isolated polypeptide may further includea pharmaceutically acceptable carrier.

The present invention also provides methods for identifying andisolating variable domains of an antibody that recognize and bind totoxin A and or toxin B comprising use of the C-TAB.G5 or C-TAB.G5.1isolated polypeptide to produce an immune response, purifying and thencharacterizing the antibodies produced in response to the C-TAB.G5 orC-TAB.G5.1 isolated polypeptide. Identified epitopes may be of use forcloning further antibodies or fragments thereof.

One aspect of the present invention is directed in part to thetreatment, the prevention, and the detection of C. difficile. In someembodiments, a subject, such as an animal, receives treatment and/orprevention and/or detection of C. difficile. In other embodiments, theanimal is a human. For example, the polypeptides of the presentinvention may be used to raise antibodies to C. difficile in vivo. Byway of further example, the polypeptides of the present invention may beused to determine if a subject produces antibodies to C. difficile. Insome embodiments, the polypeptide is used to isolate antibodies. By wayof example, polypeptides may be bound to an affinity matrix.

By way of further example, the nucleic acid of the present invention canbe used to transform and/transfect cells to recombinantly produce thepolypeptides and/or antibodies of the present invention. The nucleicacids of the present invention may also be used, for example, todetermine if a subject is infected with C. difficile. By way of example,this can be achieved using methods of radiolabeled hybridization.

By way of further example, the antibodies of the present invention canbe used to recognize an infection by C. difficile. By way of example,the antibodies can recognize native toxin A and/or toxin B as anantigen. The antibodies of the present invention can also be used tofight an infection by C. difficile. By way of example, humanizedantibodies or antibody fragments or monoclonal antibodies can employ asubject's own immune response to a C. difficile infection. By way offurther example, the antibodies of the present invention may be coupledto a cytokine or a toxin or an enzyme or a marker to assist in treatingand detecting an infection.

Further aspects of the present invention relate to diagnostic assays.The present invention is of use with many assays known in the art. Thoseskilled in the art will recognize the wide array of research based usesfor the polypeptides, nucleic acids and antibodies of the presentinvention. The polypeptides, antibodies and nucleic acids of the presentinvention may, for example, be labeled, such as with a radioactive,chemiluminescent, fluorescent and/or dye molecules. The antibodies,nucleic acids and polypeptides of the present invention lend themselvesto use assays for example DNA assays (such as southern blotting), RNAassays (such as northern blotting), protein assays (such as westernblotting), chromatographic assays (such as gas, liquid, HPLC,size-exclusion), immunoassays (such as ELISA) and structural assays(such as crystallography and NMR spectroscopy). The antibodies,polypeptides and nucleic acids of the present invention may further beused as probes. Assays which amplify the signals from a probe are alsoknown to those skilled in the art.

Kits

The present invention provides kits comprising by way of example, andnot limitation, nucleic acids encoding the C-TAB.G5 or C-TAB.G5.1isolated polypeptide, the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide,and/or antibodies against the C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide. The kits may include one or more containers andinstructions for use in accordance with any of the methods of theinvention described herein. The C-TAB.G5 or C-TAB.G5.1 isolatedpolypeptide and/or antibodies of the invention may be used in a varietyof assays including immunoassays for detecting C. difficile. In oneembodiment, the C-TAB.G5 or C-TAB.G5.1 isolated polypeptide serves tofunction as an antigen for the purposes of detecting antibody inbiological samples. The containers may be unit doses, bulk packages(e.g., multi-dose packages) or sub-unit doses. The kits of thisinvention are in suitable packaging. Also contemplated are packages foruse in combination with a specific device, such as an inhaler, nasaladministration device or an infusion device. A kit may have a sterileaccess port. The container may also have a sterile access port. Kits mayoptionally provide additional components such as buffers andinterpretive information.

The kits may be used to detect the presence of C. difficile or to detecta disease associated with C. difficile, such as CDAD. The kits may beused to prevent or treat diseases associated with C. difficile. The kitsof the present invention may also be used to alleviate the symptoms of adisease associated with C. difficile.

Without further description, it is believed that one of ordinary skillin the art can, using the preceding description and the followingillustrative examples, make and utilize the claimed invention. Thefollowing working examples therefore, specifically point out preferredembodiments of the present invention, and are not to be construed aslimiting in any way the remainder of the disclosure. All articles,publications, patents and documents referred to throughout thisapplication are hereby incorporated by reference in their entirety.

EXAMPLES Example 1: Preparation of the C-TAB.G5 and C-TAB.G5.1 IsolatedPolypeptides

This Example describes the preparation of isolated polypeptidescomprising portions of the C. difficile toxins A (CTA) and B (CTB) forexpression in E. coli cells. The method described below can be used formaking various isolated polypeptides comprising CTA and CTB. As anexample, an isolated polypeptide comprising a portion of the C-terminaldomain of CTA and a portion of the C-terminal domain of CTB isdescribed.

Example 1.1: Cloning of the C-TAB.G5 and C-TAB.G5.1 Gene Constructs

The portion of CTA gene (Accession No. YP-001087137) encoding aminoacids 2026 to 2710 of the C-terminal domain was amplified by PCR fromgenomic DNA of C. difficile strain 630 (ATCC BAA-1382) using thefollowing primers:

forward: (SEQ ID NO: 9) 5′-caccACTAGTatgaacttagtaactggatggc-3′ andreverse: (SEQ ID NO: 10) 5′-CTCGAGttagccatatatcccaggggc-3′.Amplification with the forward primer created a SpeI site, andamplification with the reverse primer created of a XhoI site.

The portion of CTB gene (Accession No: YP-00108735) encoding amino acids1850 to 2366 of the C-terminal domain was amplified b PCR using thefollowing primers:

forward: (SEQ ID NO: 11) 5′-caccATGCATatgagtttagttaatagaaaacag-3′ andreverse: (SEQ ID NO: 12) 5′-ggcCTCGAGctattcactaatcactaattgagc-3′.Amplification with the forward primer created a Nsil site, andamplification with the reverse primer created a XhoI site.

PCR reactions were performed using PCR Super-Mix (Invitrogen). The cycleconditions was 95° C. for 2 minutes, 95° C. for 45 seconds, 55° C. for50 seconds, 68° C. for 8 minutes (30 cycles), and 72° C. for 10 minutes.The PCR products were purified with Quick gene extraction kit(Invitrogen) and ligated into the PCR 2.1 TOPO vector (Invitrogen). Theligation mixtures were used to transform E. coli Mech-1 cells by heatshock. The transformants were plated on plates of ImMedia Amp Blue(Invitrogen). White colonies were picked and cultured in 15 ml tubeswith 4 ml of LB medium containing 100 μg/ml ampicillin. Cultures wereincubated overnight at 37° C. and plasmids were extracted with Quickplasmid miniprep kit (Invitrogen).

The CTA gene fragment in the PCR 2.1-TOPO/TA vector was digested withSpeI and XhoI, and the fragment was cloned into an intermediate vector,also digested with SpeI and XhoI, using T4 DNA Ligase. A linkercontaining three restriction sites (BgLII-NsiI-SacI) was then insertedat the 3′ end of the CTA gene fragment by PCR using the following set ofsynthetic primers:

forward: (SEQ ID NO: 13)5′-AGATCTATGCATGAGCTCctcgagcccaaaacgaaaggctcagc-3′ reverse:(SEQ ID NO: 14) 5′-cggtccggggccatatatcccaggggcttttactcc-3′.

The CTB gene fragment in PCR 2.1-TOPO/TB was digested with Nsil andXhoI, and the digested CTB gene fragment was ligated to the intermediatevector containing the CTA gene and linker, which was also digested withNsiI and XhoI. The CTB gene was inserted 3′ to the linker giving theconstruct sequence 5′-CTA-linker-CTB-3′. This fusion construct isreferred to as C-TAB.V1 intermediate vector.

The C-TAB.G5 gene was amplified by PCR from C-TAB.V1 intermediate vectorusing the primers:

forward: (SEQ ID NO: 15) 5′-caccCCATTGatggtaacaggagtatttaaagga reverse:(SEQ ID NO: 16) 5′-CTCGAGctattcactaatcactaattgagctg.PCR reactions were performed using PCR Super mix (Invitrogen). The cyclecondition was 95° C. for 2 minutes, 95° C. for 45 seconds, 55° C. for 50seconds, 68° C. for 4 minutes (30 cycles) and 72° C. for 10 minutes. ThePCR products were purified with Quick gene extraction kit (Invitrogen)and ligated into the PCR2.1-TOPO vector (Invitrogen). The ligationmixtures were used to transform E. coli Mech-1 cells by heat shock. Thetransformants were plated on plates of ImMedia Amp Blue (Invitrogen).White colonies were picked and cultured in 15 ml tubes with 4 ml of LBmedium containing 100 μg/ml ampicillin. Cultures were incubatedovernight at 37° C. and plasmids were extracted with Quick plasmidmini-prep kit (Invitrogen). The C-TAB.G5 fusion gene in the PCR2.1-TOPOTA vector was digested with NcoI and XhoI restriction enzyme.These C-TAB fragments were ligated into the pET28 expression vectordigested with the same restriction enzymes. This resulting constructencodes the toxin A C-terminal domain from amino acids 2272 to 2710fused to toxin B C-terminal domain from amino acids 1851 to 2366. ThepET28/C-TAB.G5 construct was transformed into E. coli BL21 (DE3) forexpression. Five colonies containing the C-TAB.G5 fusion gene wereselected for analysis.

The C-TAB.G5.1 coding sequence was obtained by codon optimization forimproved expression within an E. coli host cells. The codon usage wasadapted to the codon bias of E. coli genes. In addition, GC content wasadjusted to prolong mRNA half life; a region of very high (>80%) or verylow (<30%) GC content have been avoided. Therefore, the optimized geneallows high and stable expression rates in E. coli. The codon optimizedC-TAB.G5.1 gene was synthesized in situ and subcloned into theexpression vector pET-28b(+).

DNA Sequencing: Plasmid DNA sequences were confirmed using dyeterminator cycle sequencing chemistry with d-Rhodamine dyes. Sequencingdata were analyzed using Jellyfish software.

Example 1.2: Expression of the Recombinant C-TAB.G5 or C-TAB.G5.1 FusionProteins in E. coli

Expression of C-TAB.G5 and C-TAB.G5.1 gene constructs may be done usingstandard procedure for expression in E. coli.

Screening colonies for expression of the recombinant C-TAB fusionprotein: For the purpose of screening, colonies were picked and grown in15 ml Falcon tubes with 4 ml of LB media with 50 μg/ml kanamycin. Thetubes were cultured overnight at 37° C. with mixing at 250 rpm.Following initial growth phase, 1 ml of culture from each tube wastransferred to a 24-well tissue culture plate and expression was inducedwith 1 mM isopropyl-β-D-1-thiogalacto-puranoside (IPTG) for 3 h at 30°C. The cell pellets were collected by centrifugation at 12,000 g for 1min in microcentrifuge. Cell pellet lysates were prepared, and thesoluble fraction was assayed by SDS-PAGE and Western Blot analysis forexpression of C-TAB fusion protein. Positive clones were selected forfurther evaluation.

Batch fermentation for C-TAB.G5 expression: Seed cultures were grown infive 500 ml shake flasks each containing 150 ml Super Broth mediumsupplemented with 30 μg/ml kanamycin. Cultures were grown for 12 h at28° C. with continuous agitation at 275 rpm until OD₆₀₀ reached 2-2.5.The shake flasks were used to inoculate a fermenter containing 10 LSuper Broth. The culture was grown approximately 4.5 h at 37° C. toOD₆₀₀=3.5-4. For induction of the product expression 0.1 mM IPTG wasadded and growth continued for additional 4 h at 25° C. Then the cellswere harvested by centrifugation and the cell paste stored frozen at−70° C. A typical product specific expression rate achieved by thisfermentation process was about 200 mg/ml.

Fed-batch fermentation for C-TAB.G5.1 preparation: An aliquot of 500 μlof the glycerol stock of a seed bank (stored at −75° C.) was used toinoculate 100 ml pre-culture medium supplemented with 30 μg/ml kanamycinin a 1 L shake flask. The pre-culture was incubated at 37° C. underconstant agitation at ˜150 rpm for approximately 7 h until it reachedOD₆₀₀=1.0-2.0. 25 mL of pre-culture was used to inoculate 7 L batchfermentation medium in a standard industry 15 L fermenter equipped withprocess control system, able to perform fed-batch fermentations. 7 Lbatch culture phase was carried for 12 h at 37° C. (OD₆₀₀=12-15) untilglucose was exhausted. Glucose feed phase (biomass production) was theninitiated by an exponential feed mode at a specific growth rate constantμ=0.25/h at 37° C. for 6 h (OD₆₀₀=40-50). One hour before switching to aconstant feed phase and induction with a final concentration of 1 mMIPTG (product production), temperature was reduced to 30° C. to lowerthe risk of inclusion body formation. Product expression phase wascontinued for another 5 h with constant feed at 30° C. (OD₆₀₀=˜100),resulting in a total fermentation process time of 23 h and a finalculture volume of ˜8.2 L. A wet cell biomass of about 1.2 kg washarvested by centrifugation and stored at ≤−70° C. A typical productspecific expression rate reached by such fed-batch fermentation was upto 1.3 g/L.

Example 1.3: Purification of the Recombinant C-TAB.G5 or C-TAB.G5.1Fusion Proteins

Purification of C-TAB.G5 analytical sample: Frozen cell paste was thawedand resuspended in 10 mM citric acid/NaOH buffer at pH 5.6, and the cellslurry was passed two times through a homogenizer (GEA Niro Soavihomogenizer) at 550 bar. The suspension was centrifuged two times: onceat 13500 rpm for 30 minutes and the second time at 18000 rpm in anultracentrifuge for one hour. The supernatants were pooled, and the pHadjusted to 5.6 with 50 mM citric acid buffer pH 3. Clarified celllysates were passed over a SP fast flow column with 10 mM citricacid/NaOH buffer at pH 5.6. Proteins were eluted with a liner gradientof sodium chloride increasing from 0 to 500 mM in 20 mM NaPi. Fractionscontaining the C-TAB.G5 were pooled. The conductivity was adjusted downto 5 mS/cm with distilled H₂O. Tris was added to a 25 mM finalconcentration. The pooled fractions were passed over a DEAE fast flowcolumn. Protein was eluted with a linear gradient of sodium chlorideincreasing from 50 to 500 mM in 25 mM Tris. Again, fractions containingC-TAB.G5 were pooled and 1.5 M Na-Citrate, pH 7.5 was added to a finalconcentration of 0.4 M. The C-TAB.V1 pool was loaded onto a phenolSepharose HP column equilibrated with 25 mM Tris, 0.4 M Na-Citrate pH7.5. C-TAB.G5 fusion protein was eluted with a reducing saltconcentration in a liner gradient using 5 mM Tris, pH 7.5. All columnswere monitored by an AKTA Prime chromatography system. Purified C-TABfusion protein was buffer exchanged to PBS using a 50 K membrane.

Purification of C-TAB.G5.1 bulk preparation: Biomass was stored at −80°C. until processing. 450 g frozen cell paste (equivalent to 2.90 Lfermenter) is diluted with 4 volumes of lysis buffer (20 mM Hepes, pH7.5, ˜0.6 mS/cm) (e.g. 450 g paste+1800 mL buffer) and thawed by thisway for ˜1 h±0.5 h under mechanical agitation. Optional, remainingclumps can be resuspended using an Ultraturrax (e.g. 5 min at 8000 rpm).Cell lysis is done on a Niro Soavi Panda high homogenizer (640±25 bar, 3cycles). The lysate is cooled down to <10° C. using a heat exchanger andkept at this temperature until centrifugation. The crude cell lysate issubmitted to a batch centrifugation step (Beckmann Avanti JLA 60.25)operated at 14000 rpm (30000 g) at 4° C. for 30 min. The supernatantsare collected and pooled. The semi-liquid part of the pellet isdiscarded too, to decrease the risk of clogging the filtration step. Thepooled supernatants are then filtered through a Supercap PDH4 100/5 inchdepth filter capsule (Pall) (250 cm² effective filtration area). Theremaining lysate in the filter housing is flushed out with lysis buffer.After clarification, an aliquot of 1M Tris stock solution, pH 7.5 isadded to the lysate to a final concentration of 25 mM. The buffercomposition of final lysate is 20 mM Hepes, 25 mM Tris, pH 7.5,conductivity ˜6 mS/cm). The lysate might be still slightly turbid afterfiltration, but this does not affect the following capture step. Capturestep is performed at room temperature with DEAE Sepharose FF (GEHealthcare) in a XK50/30 column (GE Healthcare) of following dimensions:diameter 50 mm, packed bed height 20 cm, packed bed volume ˜400 mL. Theloading density is approx. 0.8 to 1.2 g biomass/mL gel. The process isrun by an Akta Explorer system (GE Healthcare) and monitored at 280 nm.Equilibration is performed at 100 cm/h with approx. 5 CV of 25 mM Tris,20 mM Hepes, 25 mM NaCl, pH 7.5, conductivity ˜5 mS/cm until pH,conductivity and 280 nm absorbance are stable. The lysate is loaded ontothe column at 75 cm/h and the flow through is discarded. When allfiltrated lysate is loaded, flow is resumed with approx. 5 CV ofequilibration buffer until the 280 nm absorbance is stabilized.Impurities are removed from the column during wash step 2 with 5 CV of25 mM Tris, 175 mM NaCl, pH 7.5, conductivity 19 mS/cm. The C-TABprotein is eluted from the column by step elution with 3 CV of 25 mMTris, 375 mM NaCl, pH 7.5, conductivity 36 mS/cm. The collection of theC-TAB containing fractions begins when 280 nm absorbance starts toincrease (usually after 1 CV) and lasts for about 0.5 to 1.0 CV. Thepooled fractions containing C-TAB can be stored at 2-8° C. over night.Intermediate purification step is done with SP-Sepharose FF (GEHealthcare) in a XK50/30 column (GE Healthcare) at room temperature withthe following dimensions: diameter 50 mm, packed bed height 20 cm,packed bed volume ˜400 mL. The maximum loading density is approx. 4-5 mgC-TAB/mL gel. The process is run by an Akta Explorer system (GEHealthcare) and monitored at 280 nm. Equilibration, washing and lineargradient elution steps are performed at a maximum flow rate of 200 cm/h(65 mL/min) unless exceeding back pressure (>4 bar) prevents it.Equilibration is performed with approx. 5-10 CV of buffer G at 200 cm/huntil pH, conductivity and 280 nm absorbance are stable. Before loading,the DEAE pool has to be adjusted to allow binding of C-TAB on SP-FFresin. DEAE pool is diluted 25 fold with SP-FF equilibration buffer (10mM citric acid, 2 mM EDTA, pH 5.5±0.1, conductivity ˜2 mS/cm) to a finalconductivity of not more than 3.5 mS/cm, pH 5.5±0.1. If necessaryadditional MilliQ water is added to achieve the desired conductivity.Note that low conductivity is very critical to allow binding of C-TABonto SP-FF. The sample is loaded onto the column at 150 cm/h and theflow through is discarded. After loading the sample, flow is resumedwith approx. 5 CV of equilibration buffer at 200 cm/h until the 280 nmabsorbance is stabilized. Elution is done by linear gradient at 100 cm/hfrom 0% equilibration buffer to 30% 20 mM sodium phosphate, 500 mM NaCl,pH 7.0 over 10 CV. Fractions are collected and pooling is performed byUV 280 nm absorbance. Pooling starts at 15% of peak maximum and ends at15% of peak maximum. The pool is immediately adjusted to 400 mM citrate(final pH 7, approx. 49 mS/cm) using a 1.5 M citrate stock solution, pH8.0. The adjusted SPFF pool should have pH 7 and approx. 49 mS/cm and isstored at 2-8° C. over night.

Polishing chromatography step is performed with Phenyl-Sepharose HP (GEHealthcare) in a XK50/30 column (GE Healthcare) at room temperature withthe following dimensions: diameter 50 mm, packed bed height 15 cm,packed bed volume ˜300 mL. The loading density is approx. 4-5 mgC-TAB/mL gel. The process is run by an Akta Explorer system (GEHealthcare) and monitored at 280 nm. Equilibration, loading, washing andelution steps are performed at a maximum flow rate of 100 cm/h (33mL/min) unless exceeding back pressure (>4 bar) prevents it. In such acase the flow rate has to be reduced. Equilibration is performed withapprox. 5-10 CV of 25 mM Tris, 400 mM sodium citrate, pH 7.5, 46 mS/cmat 100 cm/h until pH, conductivity and 280 nm absorbance are stable. Thesample is loaded onto the column at 100 cm/h and the flow through isdiscarded. After loading the sample, flow is resumed with approx. 5 CVof equilibration buffer at 100 cm/h until the 280 nm absorbance isstabilized. Elution is done by linear gradient at 100 cm/h from 100%equilibration buffer/0% 5 mM Tris, pH 7.5, 0.5 mS/cm to 100% 5 mM Tris,pH 7.5, 0.5 mS/cm over 20 CV. Fractions are collected and pooling isperformed by UV280 nm absorbance. Pooling starts at approx. 10-15% ofpeak maximum and ends at approx. 20% of peak maximum. The adjusted poolis stored at 2-8° C. over night. Preparation of final C-TAB drugsubstance protein solution is achieved by 30 kDa cut-off tangential flowfiltration (TFF, Pellicon 2 membrane, Millipore) operated at roomtemperature. The protein solution is diafiltered against formulationbuffer (20 mM Histidine, 75 mM NaCl, 5% Sucrose, 0.025% Tween®80, pH6.5) until the permeate pH equals 6.5±0.2).

Final protein concentration is adjusted to 2 mg/mL according to UVmeasurement at 280 nm using 1.566 as the specific extinction coefficientat 280 nm for C-TAB (protein conc. 1 mg/mL, 1 cm cuvette).

SDS-PAGE and Western Blot Analysis: Whole cell lysates and purifiedC-TAB.G5 or C-TAB.G5.1 fusion protein were resuspended in Nu-Page samplebuffer containing beta-mercaptoethanol and boiled for 10 min. Samples(25 μl) were loaded onto 3-8% Tris-Acetate gel. Followingelectrophoresis (150 V for 1 h), proteins were visualized by stainingthe gels with simply blue stain or used for Western blot analysis.

C-TAB.G5 or C-TAB.G5.1 specific expression was determined by Westernblot analysis using toxin-specific antibodies. Proteins were transferredat 23 V for 60 min onto a PVDF membrane using 1× Transfer buffer in 10%methanol. Membranes were blocked for 1 h at room temperature with 0.5%casein in phosphate buffered saline (PBS). Transfer membranes wereincubated for 2 hrs at room temperature with either a monoclonalantibody against Toxin B (GenWay; clone B426M) or an in-house derivedGuinea Pig polyclonal antibody against Toxin A (List Biological Labs).Washed membranes were incubated with horseradish peroxidase conjugatedanti-guinea pig IgG or anti-mouse IgG. The blots were washed and AECsubstrates were added. The blots were incubated with gentle mixing for5-10 minutes. The blots were rinsed with water to stop colordevelopment.

RBC hemagglutination: The cell binding domain of toxin A but not toxin Bhas been shown to be capable of agglutinating rabbit red blood cells(RBCs). The agglutination process is the result of the binding of toxinA to a glycan sequence found on blood antigens on rabbit RBCs. Samples(C-TAB.G5 and native toxin A) are diluted to 100 μg/ml in PBS. In aV-bottom microtiter plate, two-fold serial dilutions are prepared induplicate across the plate, starting at 100 μg/ml and leaving 50 μl ofthe dilution in each well. Fifty microliters of a 0.75% rabbit RBC/PBSsuspension is added to each well of the microtiter plate and the plateis incubated for 1 h at room temperature. Hemagglutination is indicatedby the failure to form a pellet of RBCs on the bottom of the plate. Thehemagglutination titer of a sample is represented by the concentrationof protein present in the well with the highest sample dilution in whichno RBC pellet is observed.

Example 2: Dose Titration of the Recombinant C-TAB.G5 Fusion Protein inthe Presence and Absence of Alum in Mice

This study was to determine the feasibility of an in vivo dose titrationof C-TAB.G5 with and without alum adjuvant as a C-TAB potency assay. Thealum utilized was Alydragel, (alum hydroxide, Brenntag). C57BL/6 femalemice (Charles River Labs.), aged between 8 and 9 weeks, were utilizedfor immunization. All animals received a first immunization byintramuscular (IM) injection (50 μl) into the right thigh muscle on day0. The second immunization was done by IM injection into the left thighmuscle on day 14. A total of 72 mice were divided into 12 groupsvaccinated as follows:

-   -   Group 1: PBS only    -   Group 2: 100 (154) ng C-TAB.G5    -   Group 3: 300 (462) ng C-TAB.G5    -   Group 4: 1,000 (1,540) ng C-TAB.G5    -   Group 5: 3,000 (4,620) ng C-TAB.G5    -   Group 6: 10,000 (15,400) ng C-TAB.G5    -   Group 7: PBS with 50 μg alum    -   Group 8: 10.0 (15.4) ng C-TAB.G5 with 50 μg alum OH    -   Group 9: 30.0 (46.2) ng C-TAB.G5 with 50 μg alum OH    -   Group 10: 100 (154) ng C-TAB.G5 with 50 μg alum OH    -   Group 11: 300 (462) ng C-TAB.G5 with 50 μg alum OH    -   Group 12: 1,000 (1,540) ng C-TAB.G5 with 50 μg alum OH

In this study the protein concentration was firstly determined accordingto the standard protocol Quick Start™ Bradford Protein Assay (Bio-Rad).Lately, the protein concentration (shown in parentheses) wasre-determined by UV measurement at 280 nm according to the proceduredescribed in Example 1.3. In all follow-up studies the proteinconcentration was measured by UV method.

Blood samples were collected from all animals two weeks after the firstimmunization (study day 14) and two weeks after the second immunization(study day 28). The serum was stored at −20° C. until analyzed.

Serum IgG ELISA: Serum antibodies elicited to C-TAB.G5 or C-TAB.G5.1(referred as C-TAB), toxin A and toxin B or toxoids thereof wereevaluated in an enzyme linked immunosorbent assay (ELISA). Briefly,stock solutions of 1.0 μg/ml of toxin A, toxin B or the C-TAB.G5isolated polypeptide were prepared in PBS and 100 μl were added to eachwell of a 96-well plates. After overnight incubation at 4° C., theplates were washed and blocked with 0.5% casein blocking buffer. Plateswere washed again and serial, two-fold dilutions of test sera added tothe plates. After a second overnight incubation at 4° C., plates werewashed and incubated with peroxidase-conjugated anti-mouse IgG (H+L).After a 2 hours incubation at room temperature, the plates were againwashed, peroxidase substrate(2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonate) added and colorallowed to develop for 2 h at room temperature. The reaction was stoppedby adding 50 μl of 2% SDS to the wells. Plates are read with an ELISAplate reader at an absorbance of 405 nm. Serum antibody titers arereported as the geometric mean of ELISA Units, which are the serumdilutions that results in an OD 405 nm reading of 1.0. As a negativecontrol a pool sample of pre-immune serum obtained from animals pre-bledbefore the first immunization was used to evaluate an antibody response.

Animals receiving C-TAB.G5 demonstrated a dose dependent increase inantibody titers, with the alum adjuvant allowing for significantlyimproved antibody titers at a lower dose of C-TAB.G5. FIG. 3 shows thetiters for anti C-TAB, anti-toxin A and anti-toxin B IgG. FIG. 4 shows agraphical comparison of antibody titers in the presence or absence ofalum.

Example 3: Immunogenicity and Protective Efficacy of C-TAB.G5 in Mice

This study was to evaluate the immunogenicity and protective efficacy ofC-TAB.G5 in vaccinated mice receiving a lethal challenge of C. difficiletoxin A or toxin B. Female C57BL/6 mice (Charles River Labs.), aged 6-7weeks, were utilized for this study. All animals received the firstvaccination by intramuscular (IM) injection (50 μl) into the right thighmuscle on day 0. The second vaccination was done by IM injection intothe left thigh muscle on day 14. 116 mice were divided into groupsvaccinated as follows:

-   -   Group 1: PBS only    -   Group 2: 3 μg C-TAB.G5    -   Group 3: 10 μg C-TAB.G5    -   Group 4: 30 μg C-TAB.G5    -   Group 5: 3 μg C-TAB.G5+50 μg alum OH    -   Group 6: 10 μg C-TAB.G5+50 μg alum OH    -   Group 7: 30 μg C-TAB.G5+50 μg alum OH    -   Group 8: PBS only    -   Group 9: 3 μg C-TAB.G5    -   Group 10: 10 μg C-TAB.G5    -   Group 11: 30 μg C-TAB.G5    -   Group 12: 3 μg C-TAB.G5+50 μg alum OH    -   Group 13: 10 μg C-TAB.G5+50 μg alum OH    -   Group 14: 30 μg C-TAB.G5+50 μg alum OH

Blood samples were collected from all animals two weeks after the secondimmunization (study day 28). The serum was stored at −20° C. untilanalyzed. Serum antibody titers to C-TAB, toxin A and toxin B were thendetermined by ELISA and reported as ELISA Units (EU).

FIG. 5 shows serum antibody titers to C-TAB, toxin A and toxin B in miceevaluated two weeks after the second immunization (study day 28). Thisstudy demonstrated that the C-TAB.G5 fusion protein is highlyimmunogenic in mice and is able to induce strong antibody responseagainst both toxin A and toxin B even without adding an adjuvant. TheC-TAB.G5 immunogenicity can be significantly augmented (more than a onelog) by co-delivery with alum hydroxide. The animals receiving C-TAB.G5with or without alum demonstrated 2-fold increased antibody responseover a one log dose range.

Besides evaluating antibody titers, the antibodies generated byimmunization with C-TAB.G5 were assessed for their ability to neutralizenative toxin A and B in in vitro toxin neutralization assay (TNA).

Toxin Neutralizing Antibody Assay (TNA). For in vitro analysis, 125 μlof either toxin A (5 ng/ml) or toxin B (1 ng/ml) was incubated with 125μl of serial dilutions of anti-sera obtained from immunized mice. Afterone hr of incubation at 37° C., the toxin:serum mixture was added tomicrotiter wells containing Vero cells (monkey kidney cells), and themicrotiter plates incubated for 18 hr. Incubation of either toxin A or Bwith Vero cells resulted in a change in cell morphology and a loss ofcell adherence which was measured by neutral red staining of toxintreated cells after removal of non-adherent cells. The toxinneutralization titer of a serum is reported as the serum dilution whichgives a 50% reduction in toxin activity.

The results of the TNA assay are shown in FIG. 6. The data indicate thatantibodies generated following immunization with the C-TAB.G5 alone arecapable of neutralizing the toxic activity of native toxin A but nottoxin B. When the C-TAB.G5 was co-delivered with alum, TNA titers wereaugmented with approximately 6-fold increase in anti-toxin A TNA andonly 2-fold lower titers in anti-toxin B TNA. This data indicates thatthe C-TAB.G5 isolated polypeptide not only retains the antibodyrecognition antigenic epitopes present in the native toxins, butcomprises critical antigenic epitopes required for the generation offunctional toxin neutralizing antibody. Thus, C-TAB.G5 is effective inneutralizing toxic effects of C. difficile toxin A and toxin B and,therefore, is useful in vaccination.

In addition to assessing antibody response, the ability of C-TAB.G5immunization to protect mice from a lethal challenge of native toxinswas determined. Three weeks after the second vaccination (study day 35)animals in vaccinated and non-vaccinated groups (N=8) receivedintraperitoneally (IP) a lethal dose of either 25 ng of toxin A or 50 ngof toxin B. Survival of the mice was monitored over the following 9 daysand the results are shown in FIG. 6. This experiment demonstrated thatimmunization of mice with C-TAB.G5 in the absence of the alum adjuvantwas capable of conferring 100% protection against a lethal challengewith native toxin A and 50% protection against toxin B challenge.Co-delivery of C-TAB.G5 with Alum enhanced the protective immunity totoxin B up to 100% protection. This data indicates that C-TAB.G5vaccination induces an immune response sufficient to protect mice fromthe toxic effects of both toxin A and B in the lethal challenge model.

Example 4: Evaluation of the Immunogenicity and Protective Efficacy ofC-TAB.G5 in Young and Aged Mice

This study was to compare the immune response mounted against C-TAB.G5in young and aged mice. Female C57BL/6 mice (Charles River Labs.), aged6-7 weeks and 18 months, respectively, were utilized for this study. Allanimals received the first vaccination by intramuscular (IM) injection(50 μl) into the right thigh muscle on day 0. The second vaccination wasdone by IM injection into the left thigh muscle on day 14. 192 mice weredivided into groups vaccinated as follows:

-   -   Group 1: PBS to young mice    -   Group 2: PBS to aged mice    -   Group 3: 10 μg C-TAB.G5 to young mice    -   Group 4: 30 μg C-TAB.G5 to young mice    -   Group 5: 10 μg C-TAB.G5 to aged mice    -   Group 6: 30 μg C-TAB.G5 to aged mice    -   Group 7: 10 μg C-TAB.G5+50 μg alum OH to young mice    -   Group 8: 30 μg C-TAB.G5+50 μg alum OH to young mice    -   Group 9: 10 μg C-TAB.G5+50 μg alum OH to aged mice    -   Group 10: 30 μg C-TAB.G5+50 μg alum OH to aged mice    -   Group 11: PBS to young mice    -   Group 12: PBS to aged mice    -   Group 13: 10 μg C-TAB.G5 to young mice    -   Group 14: 30 μg C-TAB.G5 to young mice    -   Group 15: 10 μg C-TAB.G5 to aged mice    -   Group 16: 30 μg C-TAB 5^(th) to aged mice    -   Group 17: 10 μg C-TAB.G5+50 μg alum OH to young mice    -   Group 18: 30 μg C-TAB.G5+50 μg alum OH to young mice    -   Group 19: 10 μg C-TAB.G5+50 μg alum OH to aged mice    -   Group 20: 30 μg C-TAB.G5+50 μg alum OH to aged mice

Three weeks after the second vaccination (study day 35) animals invaccinated and non-vaccinated groups (N=6) received a lethal challengeby intraperitoneal (IP) injection with 25 ng toxin A or 50 ng toxin B.Survival of the mice was monitored over the following 9 days.

Blood samples were collected from all animals two weeks after the firstimmunization (study day 14) and two weeks after the second immunization(study day 28). The serum was stored at −20° C. until analyzed. Serumantibody titers to C-TAB, toxin A and toxin B were then determined byand reported as ELISA Units (EU). Toxin A and toxin B neutralizingantibodies (TNA) were determined using Vero cells treated with acytotoxic amount of recombinant toxin A and toxin B.

Young animals receiving the C-TAB.G5 vaccine demonstrated significantlyhigher levels of all antibodies tested, as compare to old animals.Especially high antibody titers were obtained in young mice vaccinatedwith C-TAB.G5 in the presence of alum hydroxide (FIG. 7). Particularlysignificant improvement was achieved in toxin B TNA titer. At the sametime, there was no big difference between young and aged mice in abilityto withstand the toxin A and toxin B challenges. However, both groupsdemonstrated improved protection rate when vaccinated in the presence ofalum. FIG. 7 shows a comparison of C-TAB.G5 immunogenicity andprotective efficacy in young vs. old mice. FIG. 8 shows the kinetics ofanti-C-TAB antibody development in young and old mice.

Example 5: Comparison of the Immunogenicity and Protective Efficacy ofC-TAB.G5.1 and Toxoid A and B

This study was to compare the immunogenicity and protective efficacy ofC-TAB.G5.1, vs. toxoid A/B. The toxoid A/B used was the mixture of equalparts (1:1) of toxoid A (lot #1009132) and toxoid B (lot #1009133).Toxoid was prepared by formalin fixation and provided by TechLab. FemaleC57BL/6 mice (Charles River Labs.), aged 6-7 weeks, were utilized forthis study. All animals received the first vaccination by intramuscular(IM) injection (50 μl) into the right thigh muscle on day 0. The secondvaccination was done by IM injection into the left thigh muscle on day14. 180 mice were divided into groups vaccinated as follows:

-   -   Group 1: PBS only    -   Group 2: 10 μg C-TAB.G5.1    -   Group 3: 30 μg C-TAB.G5.1    -   Group 4: 10 μg C-TAB.G5.1+50 μg alum OH    -   Group 5: 10 μg C-TAB.G5.1+50 μg alum OH    -   Group 6: 30 μg toxoid A/B    -   Group 7: 10 μg toxoid A/B    -   Group 8: 30 μg toxoid A/B+50 μg alum OH    -   Group 9: 30 μg toxoid A/B+50 μg alum OH    -   Group 10: PBS    -   Group 11: 10 μg C-TAB.G5.1    -   Group 12: 30 μg C-TAB.G5.1    -   Group 13: 10 μg C-TAB.G5.1+50 μg alum OH    -   Group 14: 30 μg C-TAB.G5.1+50 μg alum OH    -   Group 15: 10 μg toxoid A/B    -   Group 16: 30 μg toxoid A/B    -   Group 17: 10 μg toxoid A/B+50 μg alum OH    -   Group 18: 30 μg toxoid A/B+50 μg alum OH

Three weeks after the second vaccination (study day 35) animals invaccinated and non-vaccinated groups (N=6) received a lethal challengeby intraperitoneal (IP) injection with 28 ng toxin A or 50 ng of toxinB. Survival of the mice was monitored over the following 9 days.

Blood samples were collected from all animals two weeks after the firstimmunization (study day 14) and two weeks after the second immunization(study day 28). The serum was stored at −20° C. until analyzed. Serumantibody titers to C-TAB, toxin A and toxin B were then determined byELISA and reported as ELISA Units (EU). Toxin A and toxin B neutralizingantibodies (TNA) were determined using Vero cells treated with acytotoxic amount of recombinant toxin A and toxin B.

This study demonstrates immunogenicity and protective efficacy ofC-TAB.G5.1 and toxoid A/B in mice after two vaccinations. Animalsreceiving C-TAB.G5.1 showed lower but significant anti-C-TAB antibodytiters, as compare to animals receiving toxoid A/B. Also, co-delivery ofalum greatly augmented all tested antibody responses. As a result, thelevel of anti-C-TAB and anti-toxin A antibodies achieved in animalsimmunized either with C-TAB.G5.1 or with toxoid A/B in the presence ofalum are similar. The only lower antibody titer was observed foranti-toxin B antibody when mice were immunized with C-TAB.G5.1, ascompare to mice immunized with toxoid A/B. Noteworthy, unlike theantibodies generated against C-TAB.G5.1 recognizing epitopes in theC-terminal portion of the toxin molecules, antibodies induced withtoxoid immunization were specific to the N-terminal portion of the toxinmolecules, which was read out in the anti-toxin ELISA. Thus, anti-toxinA and anti-toxin B antibodies generated in mice immunized withC-TAB.G5.1 and toxoid A/B were antibodies of different specificity and,therefore, can not be compared directly. However, the data indicatesthat antibody response to C-TAB.G5.1 immunization is significantly high,like in case of immunization with toxoids. In addition, the toxinchallenge study demonstrated that ability of C-TAB.G5.1 immunization toprotect mice against from a lethal challenge is comparable to protectionefficacy of toxoid A and B. FIG. 9 shows a comparison of theimmunogenicity of C-TAB.G5.1 and toxoid A/B. FIG. 10 shows the toxinneutralization and protection data for mice immunized with C-TAB.G5.1 ascompared to those immunized with toxoid A/B.

Example 5.1: Comparison of Antibody Titers and Protective Efficacy ofC-TAB.G5.1 in Different Immunization Regimens

This study was to compare the immunogenicity and protective efficacy ofC-TAB.G5.1 in mice receiving three doses of the vaccine in differentimmunization regimens. Female C57BL/6 mice (Charles River Labs.), aged6-7 weeks, were utilized for this study. 135 mice were divided into 14groups. All animals in groups no. 2-13 received three vaccinations byintramuscular (IM) injection (50 μl) into the right thigh muscle or leftthigh muscle in days indicated below. Mice in groups 1 and 8 did notreceived vaccination; they served as a negative control. Theimmunization was performed as follows:

Group Vaccine Immunization day (route) 1 — — 2 10 μg G5.1 0 (R), 3 (L),14 (R) 3 10 μg G5.1 + 50 μg Alum 0 (R), 3 (L), 14 (R) 4 10 μg G5.1 0(R), 7 (L), 21 (R) 5 10 μg G5.1 + 50 μg Alum 0 (R), 7 (L), 21 (R) 6 10μg G5.1 0 (R), 14 (L), 28 (R) 7 10 μg G5.1 + 50 μg Alum 0 (R), 14 (L),28 (R) 8 — — 9 10 μg G5.1 0 (R), 3 (L), 14 (R) 10 10 μg G5.1 + 50 μgAlum 0 (R), 3 (L), 14 (R) 11 10 μg G5.1 0 (R), 7 (L), 21 (R) 12 10 μgG5.1 + 50 μg Alum 0 (R), 7 (L), 21 (R) 13 10 μg G5.1 0 (R), 14 (L), 28(R) 14 10 μg G5.1 + 50 μg Alum 0 (R), 14 (L), 28 (R) (R) = right thighmuscle (L) - left thigh muscle

Blood samples were collected from all animals on study day 0, 3, 7, 14,21, 28, 35 and 42. The serum was stored at −20° C. until analyzed. Serumantibody titers to C-TAB, toxin A and toxin B were determined by ELISAand reported as ELISA Units (EU). Toxin A and toxin B neutralizingantibodies (TNA) were determined on study day 42 using Vero cellstreated with a cytotoxic amount of recombinant toxin A and toxin B.

Three weeks after the last vaccination (study day 49) animals invaccinated and non-vaccinated groups (N=8) received a lethal challengeby intraperitoneal (IP) injection with 28 ng toxin A or 50 ng toxin B.Survival of the mice was monitored over the following 9 days.

This study demonstrates that all antibody titers measured two weeksafter the third vaccination or on study day 35 and 42 are comparable inall immunization regimens, although the immunization regimen of 0/14/28shows the best antibody responses. If compare antibody titers measuredtwo weeks after the second vaccination, then the immunization regimen of0/14/28 is better than the immunization regimen of 0/7/21, and muchbetter than the immunization regimen of 0/3/14. This study confirmedthat anti-toxin A/B antibody titers are significantly enhanced when theantigen is co-injected with aluminum hydroxide (data not shown). Thestudy also shows that even two doses of the vaccine with alumadministered in two-week interval can elicit high antibody level,comparable to the level obtained after three dose vaccinations.

The level of toxin A/B neutralizing antibodies is much higher in theimmunization regimen of 0/7/21 and 0/14/28 than in the immunizationregimen of 0/3/14.

Complete protection against challenge with toxin A does not require alumin the immunization regimen of 0/7/21 and 0/14/28 but not in 0/3/14. Theimmunization regimen of 0/14/28/with alum induced a highest level ofprotection (87.5%) against toxin B challenge, while the immunizationregimen of 0/7/21 provides 37.5% of protection and 0/3/14 shows 28.6% ofprotection. Results of this study are shown in FIGS. 20A and 20B.

Example 6: Evaluation of the Immunogenicity and Protective Efficacy ofthe Recombinant C-TAB.G5.1 Fusion Protein in Hamsters

This study was to further evaluate the immunogenicity of the recombinantfusion protein C-TAB.G5.1 administered with or without adjuvant in adifferent animal model.

Female hamsters (Harlan), aged over 7 weeks and weighing between 80 and90 g were utilized for this study. All animals received the firstvaccination by bolus (50 μl) intramuscular (IM) injection into the rightthigh muscle on day 0. The second vaccination was by IM injection intothe left thigh muscle on day 14 and the third vaccination was by IMinjection on day 28. Hamsters were divided into groups (N=6) andvaccinated as follows:

-   -   Group 1: Formulation buffer only    -   Group 2: 10 μg C-TAB.G5.1    -   Group 3: 10 μg C-TAB.G5.1+100 μg alum OH    -   Group 4: 30 μg C-TAB.G5.1    -   Group 5: 30 μg C-TAB.G5.1+100 μg alum OH    -   Group 6: 100 μg C-TAB.G5.1    -   Group 7: 100 μg C-TAB.G5.1+100 μg alum OH    -   Group 10: Formulation buffer only    -   Group 11. 10 μg C-TAB.G5.1    -   Group 12. 10 μg C-TAB.G5.1+100 μg alum OH    -   Group 13. 30 μg C-TAB.G5.1    -   Group 14. 30 μg C-TAB.G5.1+100 μg alum OH    -   Group 15 100 μg C-TAB.G5.1    -   Group 16. 100 μg C-TAB.G5.1+100 μg alum OH

Two weeks after the third vaccination (study day 42) animals invaccinated and non-vaccinated groups (N=6) received a lethal challengeby intraperitoneal (IP) injection with 75 ng toxin A or 125 ng toxin B.An extra 12 hamsters were used for a dose titration of toxin A or toxinB challenge on the day 44. Survival of the hamsters was monitored overthe following 8 days.

Blood samples were collected from all animals two weeks after the firstimmunization (study day 14), after the second immunization (study day28) and the third immunization (study day 35). The serum was stored at−20° C. until analyzed. Serum antibody titers to C-TAB, toxin A andtoxin B were then determined by ELISA and reported as ELISA Units (EU).Toxin A and toxin B neutralizing antibodies (TNA) were determined usingVero cells treated with a cytotoxic amount of recombinant toxin A andtoxin B.

This study demonstrated that hamsters, similarly to mice, were ablepositively respond to the C-TAB.G5.1 vaccination. Animals receivingC-TAB.G5.1 demonstrated a dose dependent increase in all tested antibodytiters, while the alum adjuvant significantly improved antibody titersat all doses of C-TAB.G5. The highest antibody titers were observed twoweeks after the second shots (study day 28). FIGS. 11A-11C show antibodytiters for each group of immunized hamsters. FIG. 12 shows the kineticsof anti-C-TAB antibody development in hamsters immunized with C-TAB.G5in the presence or absence of alum hydroxide.

The results of the TNA assay are shown in FIG. 13. These results aresimilar to those obtained for mice and indicate that antibody generatedagainst the C-TAB.G5.1 fusion protein in hamsters are effective inneutralizing toxic effects of C. difficile toxin A and toxin B.

FIG. 13 also shows protection data for hamsters immunized withC-TAB.G5.1 following a lethal toxin challenge. High protection wasachieved even by vaccination with C-TAB.G5.1 in the absence of theadjuvant. The protection level was improved to 100% by adding alum tothe vaccine.

Example 7: The Protective Efficacy of the C-TAB.G5.1 Fusion ProteinAgainst a C. difficile Spore Challenge in Clindamycin-Treated Hamsters

Following antibiotic treatment C. difficile can colonize the gut and, iftoxigenic, may cause an antibiotic associated diarrhea. C. difficileassociated disease (CDAD) of humans is modeled in hamsters usingclindamycin to make the animals susceptible to colonization, diarrheaand death, usually within a few days after seeding with a toxigenicstrain. To assess the efficacy of the C-TAB.G5.1 vaccine, vaccinated andnon-vaccinated hamsters were challenged with clindamycin and C.difficile strain 630. 100 μg of C-TAB.G5.1 was mixed with 125 μgalum-hydroxide adjuvant. Female adult hamsters weighing ˜100 g received3 vaccinations by intramuscular (IM) injection on days 0, 14 and 28. Theplacebo was PBS. 48 hamsters were divided into groups of 8 as vaccinatedas follows:

-   -   Group 1: PBS only+10² spore challenge    -   Group 2: C-TAB.G5.1+10² spore challenge    -   Group 3: PBS only+10³ spore challenge    -   Group 4: C-TAB.G5.1+10² spore challenge    -   Group 5: PBS only+10⁴ spore challenge    -   Group 6: C-TAB.G5.1+10⁴ spore challenge

On day 42 all animals in all groups received an oral dose of 10 mgclindamycin phosphate/kg body weight. On day 43 all animals in allgroups were dosed by oral gavage with washed spores of C. difficilestrain 630. Three levels of spore challenge were used (˜10², 10³ and10⁴). Observation, but no treatment, continued until day 54. At studytermination, all surviving animals were disease free for ≥5 days.

Blood samples were drawn to obtain serum for serological studies on day0, 14, 28, 42 and day 54 (end of study). Feces were collected on days 1and 42, directly from the anus of the hamsters, or if needed, from amongthe bedding.

Results are shown on FIG. 14 demonstrating survival curves after sporechallenge in hamsters. Survival data was plotted as Kaplan-Meiersurvival fit curves and statistical analysis was done using a log rankanalysis. At all spore doses, 100% survival of hamsters in thevaccinated group was observed and survival was significantly enhancedwhen compared to the placebo group: p=0.0245 at 10² spores, p=0.0006 at10³ spores, p<0.0001 at 10⁴ spores.

Example 8: Immunogenicity and Protection Efficacy of C-TAB.G5.1 inMonkeys

This study was to evaluate the immunogenicity and protection ofC-TAB.G5.1 in cynomolgus monkeys. Six female cynomolgus monkeys, agedbetween 4 and 6 years and weighing between 2 and 4 kg, were used forthis study. Two groups of three monkeys were arranged, the first group(Group 1) receiving 200 μg of C-TAB.G5.1 and the second (Group 2)receiving 200 μg of C-TAB.G5.1 and 250 μg alum. As alum adjuvantRehydragel (Reheis, lot #534401, dilute in PBS to 2 mg/ml) was used.Before blood collection or immunization, animals were shaved (ifnecessary).

The 1^(st) (study day 0) and 3^(rd) (study day 28) immunizations wereinjected on the left arm (deltoid), the 2^(nd) immunization (study day14) was injected to the right arm (deltoid). Group 1 received 200 μgC-TAB.G5.1 alone in 0.5 ml 1×PBS by IM injection and Group 2 received200 μg C-TAB.G5.1 with 250 μg alum in 0.5 ml 1×PBS by IM injection.

At the established time points (study days 0, 14, 28 and 42), 2-3 mL ofwhole blood was obtained by standard methods into serum separator tubes.Serum samples were frozen at approximately −20° C. ELISA method was thenused to assess anti-C-TAB, anti-toxin A and anti-toxin B IgG titers.Antibody titers were presented in ELISA Units (EU).

FIG. 15 shows that increased doses of C-TAB.G5.1 lead to increasedantibody production recognizing all three proteins, while the presenceof alum significantly improved antibody levels. The highest antibodytiters were observed with two vaccinations on day 42. These data clearlyindicate feasibility of using the recombinant C-TAB.G5 or C-TAB.G5.1fusion proteins for vaccination subjects in need thereof.

Example 9: Comparison of the Immunogenicity of C-TAB.G5 and C-TAB.G5.1

This study was to compare the immunogenicity of C-TAB.G5 and C-TAB.G5.1as well as the effect of two different buffers in which the C-TAB wasdelivered in. C57BL/6 female mice (Charles River Labs.), aged between 8and 9 weeks, were utilized for immunization. All animals received thefirst immunization by intramuscular (IM) injection (50 μl) into theright thigh muscle on day 0. The second immunization was done by IMinjection into the left thigh muscle on day 14. A total of 72 mice weredivided into 12 groups vaccinated as follows:

-   -   Group 1: 1 μg C-TAB.G5 in PBS    -   Group 2: 3 μg C-TAB.G5 in PBS    -   Group 3: 10 μg C-TAB.G5 in PBS    -   Group 4: 30 μg C-TAB.G5 in PBS    -   Group 5: 1 μg C-TAB.G5 in histidine buffer    -   Group 6: 3 μg C-TAB.G5 in histidine buffer    -   Group 7: 10 μg C-TAB.G5 in histidine buffer    -   Group 8: 30 μg C-TAB.G5 in histidine buffer    -   Group 9: 1 μg C-TAB.G5.1 in histidine buffer    -   Group 10: 3 μg C-TAB.G5.1 in histidine buffer    -   Group 11: 10 μg C-TAB.G5.1 in histidine buffer    -   Group 12: 30 μg C-TAB.G5.1 in histidine buffer

Blood samples were collected from all animals two weeks after the secondimmunization (study day 28). The serum was stored at −20° C. untilanalyzed. Serum antibody titers to C-TAB, toxin A and toxin B weredetermined by ELISA and reported as ELISA Units.

FIG. 16 shows that all antibody titers (anti-C-TAB, anti-toxin A andanti-toxin B) were not significantly different (as revealed by T-testanalysis) over 1-30 μg dose range for three vaccine formulations.Slightly higher antibody production was achieved with C-TAB.G5formulation in histidine buffer, as compare to PBS. No significantdifference was observed between immunization with C-TAB.G5 andC-TAB.G5.1 histidine formulations. Thus, this study demonstrates theequal immunogenicity of C-TAB.G5 and C-TAB.G5.1 constructs.

Example 10: Preparation and Evaluation of the Alternative C-TABNCTB andC-TADCTB Fusion Proteins

This Example describes the preparation of two other fusion proteinscomprising one portion of the C-terminal domain of CTA and two portionsof the C-terminal domain of CTB derived from C. difficile VPI-10463strain. The C-TABNCTB fusion protein (SEQ ID NO: 18) comprises, likeC-TAB.G5, 19 repeating units of CTA (amino acids 2272-2710), 23repeating units of CTB (amino acids 1850-2366), plus additional 10repeats of CTB (amino acids 1834-2057) fused to the C-terminus of CTB.The C-TADCTB fusion protein (SEQ ID NO: 20) comprises C-TAB.G5 sequence(19 repeats of CTA and 23 repeats of CTB) plus additional 24 repeatingunits of CTB (amino acids 1834-2366) fused to the C-terminus ofC-TAB.G5. Thus, C-TADCTB comprises a double portion of repeating unitsof CTB. Cloning of the C-TABNCTB and C-TADCTB gene constructs was donein a way similar to that described in Example 1. 1 The recombinantfusion proteins were expressed in E. coli cells and purified usingstandard procedure as described in Example 1.2. The isolatedpolypeptides were evaluated in the immunogenicity and protection studiesin animals.

Example 10.1: Comparison of the Immunogenicity and Protective Efficacyof C-TAB.G5, C-TABNCTB and C-TADCTB in Mice

This study was to compare the immunogenicity and protective efficacy ofC-TAB.G5, C-TABNCTB and C-TADCTB in mice vaccinated with five antigendoses over a two log range. Female C57BL/6 mice (Charles River Labs.),aged 6-7 weeks, were utilized for this study. All animals received twovaccinations: the first one by intramuscular (IM) injection (50 μl) intothe right thigh muscle on day 0. The second vaccination was done by IMinjection into the left thigh muscle on day 14. All immunizations weredone in the absence of alum. Blood samples were collected two weeksafter the second immunization (study day 28). The serum was stored at−20° C. until analyzed. Serum antibody titers to C-TAB, toxin A andtoxin B were determined by ELISA and reported as ELISA Units (EU) shownin FIG. 17.

This study demonstrated that the alternative fusion proteins C-TADCTBand C-TABNCTB, as well as C-TAB.G5, are highly immunogenic and able toinduce strong antibody response against both toxin A and toxin B evenwithout adding an adjuvant.

In addition to assessing antibody response, the ability of C-TADCTB andC-TABNCTB immunization to protect mice from a lethal challenge of nativetoxin B was determined. Three weeks after the second vaccination (studyday 35) animals in vaccinated and non-vaccinated groups (N=6) receivedintraperitoneally (IP) a lethal dose of 50 ng of toxin B. Survival ofthe mice was monitored over the following 9 days and the results areshown in FIG. 18. This experiment demonstrated that immunization of micewith 33 μg of C-TADCTB in the absence of alum was capable of conferring100% protection against a lethal challenge with native toxin B, whilethe same dose of C-TAB.G5 and C-TABNCTB induces only partial protection.This data indicates that, similarly to C-TAB.G5, two other fusionproteins C-TADCTB and C-TABNCTB may be protective against the lethalchallenge with the native toxin.

Example 10.2: Comparison of the Immunogenicity and Protective Efficacyof C-TAB.G5.1 and C-TADCTB in Hamsters

This study was to further evaluate the immunogenicity of the alternativefusion protein C-TADCTB administered with or without alum adjuvant in adifferent animal model.

The study was designed as described in Example 6: female hamsters werevaccinated three times by IM injection (study day 0, 14 and 28) in thepresence or absence of 100 μg alum hydroxide. Two weeks after the thirdvaccination (study day 42) all animals received a lethal challenge byintraperitoneal (IP) injection with 75 ng toxin A or 125 ng toxin B.Blood samples were collected on study day 14, 28 and 35 and serumantibody titers to C-TAB, toxin A and toxin B were determined by ELISA.Toxin A and toxin B neutralizing antibodies (TNA) were measured in day35 sera. Survival of the hamsters was monitored and reported as % ofprotection.

This study demonstrated that the fusion protein C-TADCTB can induceanti-toxin antibody response in hamsters, similarly to mice. The alumadjuvant significantly improved all tested antibody titers. The resultsof the TNA assay shown in FIG. 19 indicate that antibody generatedagainst C-TADCTB are effective in neutralizing toxic effects of C.difficile toxin A and toxin B. FIG. 19 also demonstrates comparison ofprotection data for hamsters immunized either with C-TAB.G5.1 or withC-TADCTB. High protection was achieved by vaccination with bothrecombinant fusion proteins.

Example 11: An Open-Label Phase 1 Study Assessing the Safety,Immunogenicity and Dose Response of a Pharmaceutical CompositionComprising C-TAB.G5.1

The pharmaceutical composition comprising C-TAB.G5.1, a recombinantfusion protein consisting of truncated Clostridium difficile (C.difficile) Toxin A and Toxin B, which will be administered at threedifferent doses: 20 μg with Al(OH)₃ (alum), 75 and 200 μg without orwith Al(OH)₃, respectively, intramuscular (IM) injection, threevaccinations on Day 0, 7 and 21.

Study Objectives

Primary:

-   -   To investigate the safety and tolerability of a pharmaceutical        composition comprising C-TAB.G5.1 up to 6 months after the third        vaccination.

Secondary:

-   -   To investigate the immune response measured against the vaccine        antigen C-TAB.G5.1 and the native Toxins A and B of C. difficile        to three different doses and two formulations on Days 0, 7, 14,        21, 28, 113, 201 after the first vaccination to obtain a first        indication of the optimal dose and formulation.    -   To investigate the capacity of C-TAB.G5.1 vaccine-induced IgG        antibodies to neutralize C. difficile Toxins A and B in vitro.        Study Design

This is an open-label, partially randomized, dose escalation Phase 1study which will consist of a part A in healthy adults aged between ≥18and <65 years and a part B in healthy elderly ≥65 years, the latter agegroup being the most vulnerable population to suffer from C. difficileinfections. Part A will be conducted with vaccination schedule Day 0, 7and 21 in five treatment groups of 12 healthy adult subjects to studysafety and dose response to 20 μg C-TAB.G5.1 vaccine with adjuvant, andto 75 μg and 200 μg of C-TAB.G5.1 vaccine with or without adjuvant,respectively. Safety and immunogenicity will be analyzed after all adultsubjects of part A have received the third vaccination, all safety datawill be reviewed by a Data Safety Monitoring Board (DSMB) prior toenrollment of subjects from part B. In case non-safe or futile treatmentgroups (i.e., doses that do not induce considerable IgG responses) areidentified during the interim analysis, these treatment groups will bedropped and not carried forward to part B.

Part B of the study will seek dose confirmation in the elderlypopulation. Accordingly, Part B will be conducted in 5 treatment groupsof 20 elderly healthy subjects per group. Vaccination schedule Day 0, 7and 21 will be applied. This study design will allow to compare doseresponses in both adults and elderly. The latter age group will be themajor target population for a C. difficile vaccine, representing themost vulnerable population for the two target indications in thedevelopment pathway of a C. difficile vaccine, i.e. prevention ofrecurrent C. difficile diarrhea and prevention of primary C. difficileinfection in an age-based or age-risk based preventive vaccinationapproach. However, elderly subjects might be less responsive tovaccination than young adults; thus, dose confirmation in the elderlytarget population from an early development stage on is required. Aninterim analysis after all adults from part A have been vaccinated willallow to drop non-safe or doses/formulations which do not induceconsiderable IgG responses in adults in order to mitigate the risk ofexposing subjects in the elderly group to potentially unsafe or futiledoses (e.g. lowest dose) and/or formulations (e.g. non-adjuvantedformulation) of the vaccine.The C-TAB.G5.1 vaccine is an aqueous solution of C-TAB.G5.1 in 20 mML-Histidine, 75 mM NaCl, 5% Sucrose, 0.025% Tween®80; pH6.5 produced bystandard methods.

SEQUENCES: SEQ ID Name NOs: Sequences C-TAB.G5 1ATGGTAACAGGAGTATTTAAAGGACCTAATGGATTTGAGTATTTTGC (nucleic acidACCTGCTAATACTCACAATAATAACATAGAAGGTCAGGCTATAGTTT sequence)ACCAGAACAAATTCTTAACTTTGAATGGCAAAAAATATTATTTTGATAATGACTCAAAAGCAGTTACTGGATGGCAAACCATTGATGGTAAAAAATATTACTTTAATCTTAACACTGCTGAAGCAGCTACTGGATGGCAAACTATTGATGGTAAAAAATATTACTTTAATCTTAACACTGCTGAAGCAGCTACTGGATGGCAAACTATTGATGGTAAAAAATATTACTTTAATACTAACACTTTCATAGCCTCAACTGGTTATACAAGTATTAATGGTAAACATTTTTATTTTAATACTGATGGTATTATGCAGATAGGAGTGTTTAAAGGACCTAATGGATTTGAATACTTTGCACCTGCTAATACTCATAATAACAACATAGAAGGTCAAGCTATACTTTACCAAAATAAATTCTTAACTTTGAATGGTAAAAAATATTACTTTGGTAGTGACTCAAAAGCAGTTACCGGATTGCGAACTATTGATGGTAAAAAATATTACTTTAATACTAACACTGCTGTTGCAGTTACTGGATGGCAAACTATTAATGGTAAAAAATACTACTTTAATACTAACACTTCTATAGCTTCAACTGGTTATACAATTATTAGTGGTAAACATTTTTATTTTAATACTGATGGTATTATGCAGATAGGAGTGTTTAAAGGACCTGATGGATTTGAATACTTTGCACCTGCTAATACAGATGCTAACAATATAGAAGGTCAAGCTATACGTTATCAAAATAGATTCCTATATTTACATGACAATATATATTATTTTGGTAATAATTCAAAAGCAGCTACTGGTTGGGTAACTATTGATGGTAATAGATATTACTTCGAGCCTAATACAGCTATGGGTGCGAATGGTTATAAAACTATTGATAATAAAAATTTTTACTTTAGAAATGGTTTACCTCAGATAGGAGTGTTTAAAGGGTCTAATGGATTTGAATACTTTGCACCTGCTAATACGGATGCTAACAATATAGAAGGTCAAGCTATACGTTATCAAAATAGATTCCTACATTTACTTGGAAAAATATATTACTTTGGTAATAATTCAAAAGCAGTTACTGGATGGCAAACTATTAATGGTAAAGTATATTACTTTATGCCTGATACTGCTATGGCTGCAGCTGGTGGACTTTTCGAGATTGATGGTGTTATATATTTCTTTGGTGTTGATGGAGTAAAAGCCCCTGGGATATATGGCAGATCTATGCATAATTTGATAACTGGATTTGTGACTGTAGGCGATGATAAATACTACTTTAATCCAATTAATGGTGGAGCTGCTTCAATTGGAGAGACAATAATTGATGACAAAAATTATTATTTCAACCAAAGTGGAGTGTTACAAACAGGTGTATTTAGTACAGAAGATGGATTTAAATATTTTGCCCCAGCTAATACACTTGATGAAAACCTAGAAGGAGAAGCAATTGATTTTACTGGAAAATTAATTATTGACGAAAATATTTATTATTTTGATGATAATTATAGAGGAGCTGTAGAATGGAAAGAATTAGATGGTGAAATGCACTATTTTAGCCCAGAAACAGGTAAAGCTTTTAAAGGTCTAAATCAAATAGGTGATTATAAATACTATTTCAATTCTGATGGAGTTATGCAAAAAGGATTTGTTAGTATAAATGATAATAAACACTATTTTGATGATTCTGGTGTTATGAAAGTAGGTTACACTGAAATAGATGGCAAGCATTTCTACTTTGCTGAAAACGGAGAAATGCAAATAGGAGTATTTAATACAGAAGATGGATTTAAATATTTTGCTCATCATAATGAAGATTTAGGAAATGAAGAAGGTGAAGAAATCTCATATTCTGGTATATTAAATTTCAATAATAAAATTTACTATTTTGATGATTCATTTACAGCTGTAGTTGGATGGAAAGATTTAGAGGATGGTTCAAAGTATTATTTTGATGAAGATACAGCAGAAGCATATATAGGTTTGTCATTAATAAATGATGGTCAATATTATTTTAATGATGATGGAATTATGCAAGTTGGATTTGTCACTATAAATGATAAAGTCTTCTACTTCTCTGACTCTGGAATTATAGAATCTGGAGTACAAAACATAGATGACAATTATTTCTATATAGATGATAATGGTATAGTTCAAATTGGTGTATTTGATACTTCAGATGGATATAAATATTTTGCACCTGCTAATACTGTAAATGATAATATTTACGGACAAGCAGTTGAATATAGTGGTTTAGTTAGAGTTGGGGAAGATGTATATTATTTTGGAGAAACATATACAATTGAGACTGGATGGATATATGATATGGAAAATGAAAGTGATAAATATTATTTCAATCCAGAAACTAAAAAAGCATGCAAAGGTATTAATTTAATTGATGATATAAAATATTATTTTGATGAGAAGGGCATAATGAGAACGGGTCTTATATCATTTGAAAATAATAATTATTACTTTAATGAGAATGGTGAAATGCAATTTGGTTATATAAATATAGAAGATAAGATGTTCTATTTTGGTGAAGATGGTGTCATGCAGATTGGAGTATTTAATACACCAGATGGATTTAAATACTTTGCACATCAAAATACTTTGGATGAGAATTTTGAGGGAGAATCAATAAACTATACTGGTTGGTTAGATTTAGATGAAAAGAGATATTATTTTACAGATGAATATATTGCAGCAACTGGTTCAGTTATTATTGATGGTGAGGAGTATTATTTTGATCCTGATACAGCTCAATTAGTGAT TAGTGAATAG C-TAB.G5 2MVTGVFKGPNGFEYFAPANTHNNNIEGQAIVYQNKFLTLNGKKYYFD  (amino acidNDSKAVTGWQTIDGKKYYFNLNTAEAATGWQTIDGKKYYFNLNTAEA  sequence)ATGWQTIDGKKYYFNTNTFIASTGYTSINGKHFYFNTDGIMQIGVFK GPNGFEYFAPANTHNNNIEGQAILYQNKFLTLNGKKYYFGSDSKAVTGLRTIDGKKYYFNTNTAVAVTGWQTINGKKYYFNTNTSIASTGYTIISGKHFYFNTDGIMQIGVFKGPDGFEYFAPANTDANNIEGQAIRYQNRFLYLHDNIYYFGNNSKAATGWVTIDGNRYYFEPNTAMGANGYKTIDNKNFYFRNGLPQIGVFKGSNGFEYFAPANTDANNIEGQAIRYQNRFLHLLGKIYYFGNNSKAVTGWQTINGKVYYFMPDTAMAAAGGLFEIDGVIYFFGVDGVKAPGIYGRSMHNLITGFVTVGDDKYYFNPINGGAASIGETIIDDKNYYFNQSGVLQTGVFSTEDGFKYFAPANTLDENLEGEAIDFTGKLIIDENIYYFDDNYRGAVEWKELDGEMHYFSPETGKAFKGLNQIGDYKYYFNSDGVMQKGFVSINDNKHYFDDSGVMKVGYTEIDGKHFYFAENGEMQIGVFNTEDGFKYFAHHNEDLGNEEGEEISYSGILNFNNKIYYFDDSFTAVVGWKDLEDGSKYYFDEDTAEAYIGLSLINDGQYYFNDDGIMQVGFVTINDKVFYFSDSGIIESGVQNIDDNYFYIDDNGIVQIGVFDTSDGYKYFAPANTVNDNIYGQAVEYSGLVRVGEDVYYFGETYTIETGWIYDMENESDKYYFNPETKKACKGINLIDDIKYYFDEKGIMRTGLISFENNNYYFNENGEMQFGYINIEDKMFYFGEDGVMQIGVFNTPDGFKYFAHQNTLDENFEGESINYTGWLDLDEKRYYFTDEYIAATGSVII DGEEYYFDPDTAQLVISEC-TAB.G5.1 3 CCATGGTTACAGGTGTTTTCAAAGGTCCGAACGGCTTTGAATATTTT (nucleic acid GCACCGGCAAATACCCACAATAATAATATTGAAGGCCAGGCCATCGT sequence)GTATCAGAATAAATTTCTGACCCTGAACGGCAAAAAATACTATTTCGATAACGATAGCAAAGCAGTTACCGGTTGGCAAACCATTGATGGCAAAAAATATTACTTCAACCTGAATACCGCAGAAGCAGCAACCGGCTGGCAGACGATCGACGGTAAAAAGTACTATTTTAACCTGAACACAGCCGAAGCCGCTACAGGCTGGCAGACAATAGATGGGAAGAAGTATTATTTTAATACCAATACCTTTATTGCCAGCACCGGCTATACCAGCATTAATGGCAAACACTTCTATTTTAACACCGATGGTATTATGCAGATCGGTGTGTTTAAGGGCCCTAATGGTTTTGAGTACTTCGCTCCGGCTAATACCGATGCAAATAACATCGAAGGTCAGGCAATTCTGTACCAGAACAAATTTTTAACGCTGAACGGTAAGAAATATTACTTTGGTAGCGATTCAAAAGCCGTTACCGGTCTGCGTACGATCGACGGCAAGAAATATTATTTCAATACAAACACCGCAGTTGCCGTGACAGGTTGGCAGACGATAAATGGTAAGAAGTACTACTTCAACACCAATACCAGCATTGCAAGTACCGGTTATACCATTATCAGCGGCAAACACTTTTACTTCAATACAGACGGCATTATGCAGATTGGCGTTTTCAAAGGTCCGGATGGTTTCGAGTACTTTGCCCCTGCAAATACAGATGCAAACAATATTGAGGGACAGGCAATTCGCTATCAGAATCGTTTTCTGTATCTGCACGATAACATCTATTACTTCGGCAATAATTCAAAAGCAGCCACCGGTTGGGTTACAATTGATGGTAATCGTTATTACTTTGAGCCGAATACCGCAATGGGTGCAAATGGTTATAAAACCATCGATAACAAAAATTTTTATTTCCGCAACGGTCTGCCGCAGATTGGTGTTTTTAAGGGTAGCAATGGCTTCGAGTATTTTGCGCCAGCCAACACCGATGCCAACAACATTGAAGGCCAAGCGATTCGTTATCAAAACCGCTTTCTGCATCTGCTGGGCAAAATTTATTACTTTGGCAACAATAGCAAAGCGGTGACGGGCTGGCAAACCATTAACGGTAAAGTTTATTATTTCATGCCGGATACCGCTATGGCAGCAGCCGGTGGTCTGTTTGAAATTGATGGCGTGATTTATTTTTTTGGCGTGGATGGTGTTAAAGCACCGGGTATTTATGGTCGTAGCATGCATAATCTGATTACCGGTTTTGTTACCGTGGGCGACGATAAATACTACTTTAATCCGATTAATGGTGGTGCAGCAAGCATTGGTGAAACCATTATCGATGACAAAAACTATTATTTTAACCAGAGCGGTGTTCTGCAGACAGGTGTTTTTAGCACCGAAGATGGCTTCAAATATTTTGCTCCTGCGAATACACTGGATGAAAATCTGGAAGGTGAAGCAATTGATTTTACCGGCAAACTGATCATCGACGAGAACATCTACTATTTTGATGATAATTATCGCGGTGCCGTGGAATGGAAAGAACTGGATGGTGAAATGCACTATTTTAGTCCGGAAACCGGTAAAGCCTTTAAAGGTCTGAATCAGATCGGCGATTACAAGTATTACTTTAATTCAGATGGCGTGATGCAGAAAGGCTTTGTGAGCATTAACGACAACAAACACTATTTTGACGACAGCGGTGTGATGAAAGTGGGTTATACCGAAATCGACGGGAAACATTTTTATTTTGCCGAAAACGGCGAAATGCAGATTGGAGTATTTAATACCGAGGACGGCTTTAAATACTTTGCCCATCATAATGAAGATCTGGGTAATGAAGAAGGCGAAGAAATTAGCTATAGCGGCATTCTGAATTTTAATAACAAGATCTATTATTTCGATGATAGCTTCACCGCAGTTGTTGGTTGGAAAGATCTGGAAGATGGCAGCAAATATTATTTTGATGAAGATACCGCAGAGGCCTATATTGGTCTGAGCCTGATTAATGATGGCCAGTATTATTTCAACGATGATGGTATCATGCAGGTTGGTTTTGTGACCATCAACGATAAAGTGTTCTATTTCAGCGATAGCGGCATTATTGAAAGCGGTGTTCAGAACATCGACGATAACTATTTCTACATCGATGATAACGGTATTGTTCAGATTGGCGTGTTTGATACCTCCGATGGTTATAAATATTTCGCACCAGCCAATACCGTGAACGATAATATTTATGGTCAGGCAGTTGAATATTCAGGTCTGGTTCGTGTTGGCGAAGATGTTTATTATTTTGGCGAAACCTATACCATTGAAACCGGCTGGATCTATGATATGGAAAACGAGAGCGACAAGTACTATTTCAATCCGGAAACGAAAAAAGCCTGCAAAGGCATTAATCTGATCGACGATATTAAGTACTACTTTGACGAAAAAGGCATTATGCGTACCGGTCTGATTAGCTTTGAGAACAACAACTATTACTTCAATGAGAACGGTGAGATGCAGTTTGGCTATATCAACATCGAGGACAAAATGTTTTATTTTGGTGAGGACGGTGTGATGCAGATAGGGGTTTTTAATACACCGGATGGGTTTAAGTATTTTGCACATCAGAACACCCTGGATGAAAACTTTGAAGGCGAAAGCATTAATTATACCGGTTGGCTGGATCTGGATGAGAAACGTTATTATTTCACCGACGAATACATTGCAGCAACCGGTAGCGTTATTATTGATGGTGAGGAATATTACTTCGATCCGGATACAGCACAGCTGGTT ATTAGCGAATAACTCGAGC-TAB.G5.1 4 VTGVFKGPNGFEYFAPANTHNNNIEGQAIVYQNKFLTLNGKKYYFDN (amino acid DSKAVTGWQTIDGKKYYFNLNTAEAATGWQTIDGKKYYFNLNTAEAA  sequence)TGWQTIDGKKYYFNTNTFIASTGYTSINGKHFYFNTDGIMQIGVFKG PNGFEYFAPANTDANNIEGQAILYQNKFLTLNGKKYYFGSDSKAVTGLRTIDGKKYYFNTNTAVAVTGWQTINGKKYYFNTNTSIASTGYTIISGKHFYFNTDGIMQIGVFKGPDGFEYFAPANTDANNIEGQAIRYQNRFLYLHDNIYYFGNNSKAATGWVTIDGNRYYFEPNTAMGANGYKTIDNKNFYFRNGLPQIGVFKGSNGFEYFAPANTDANNIEGQAIRYQNRFLHLLGKIYYFGNNSKAVTGWQTINGKVYYFMPDTAMAAAGGLFEIDGVIYFFGVDGVKAPGIYGRSMHNLITGFVTVGDDKYYFNPINGGAASIGETIIDDKNYYFNQSGVLQTGVFSTEDGFKYFAPANTLDENLEGEAIDFTGKLIIDENIYYFDDNYRGAVEWKELDGEMHYFSPETGKAFKGLNQIGDYKYYFNSDGVMQKGFVSINDNKHYFDDSGVMKVGYTEIDGKHFYFAENGEMQIGVFNTEDGFKYFAHHNEDLGNEEGEEISYSGILNFNNKIYYFDDSFTAVVGWKDLEDGSKYYFDEDTAEAYIGLSLINDGQYYFNDDGIMQVGFVTINDKVFYFSDSGIIESGVQNIDDNYFYIDDNGIVQIGVFDTSDGYKYFAPANTVNDNIYGQAVEYSGLVRVGEDVYYFGETYTIETGWIYDMENESDKYYFNPETKKACKGINLIDDIKYYFDEKGIMRTGLISFENNNYYFNENGEMQFGYINIEDKMFYFGEDGVMQIGVFNTPDGFKYFAHQNTLDENFEGESINYTGWLDLDEKRYYFTDEYIAATGSVIID GEEYYFDPDTAQLVISENucleic acid 5 atgtctttaatatctaaagaagagttaataaaactcgcatatagcatsequence of tagaccaagagaaaatgagtataaaactatactaactaatttagacg  trdAaatataataagttaactacaaacaataatgaaaataaatatttacaa  (strain 630)ttaaaaaaactaaatgaatcaattgatgtttttatgaataaatataaaacttcaagcagaaatagagcactctctaatctaaaaaaagatatattaaaagaagtaattcttattaaaaattccaatacaagccctgtagaaaaaaatttacattttgtatggataggtggagaagtcagtgatattgctcttgaatacataaaacaatgggctgatattaatgcagaatataatattaaactgtggtatgatagtgaagcattcttagtaaatacactaaaaaaggctatagttgaatcttctaccactgaagcattacagctactagaggaagagattcaaaatcctcaatttgataatatgaaattttacaaaaaaaggatggaatttatatatgatagacaaaaaaggtttataaattattataaatctcaaatcaataaacctacagtacctacaatagatgatattataaagtctcatctagtatctgaatataatagagatgaaactgtattagaatcatatagaacaaattctttgagaaaaataaatagtaatcatgggatagatatcagggctaatagtttgtttacagaacaagagttattaaatatttatagtcaggagttgttaaatcgtggaaatttagctgcagcatctgacatagtaagattattagccctaaaaaattttggcggagtatatttagatgttgatatgcttccaggtattcactctgatttatttaaaacaatatctagacctagctctattggactagaccgttgggaaatgataaaattagaggctattatgaagtataaaaaatatataaataattatacatcagaaaactttgataaacttgatcaacaattaaaagataattttaaactcattatagaaagtaaaagtgaaaaatctgagatattttctaaattagaaaatttaaatgtatctgatcttgaaattaaaatagctttcgctttaggcagtgttataaatcaagccttgatatcaaaacaaggttcatatcttactaacctagtaatagaacaagtaaaaaatagatatcaatttttaaaccaacaccttaacccagccatagagtctgataataacttcacagatactactaaaatttttcatgattcattatttaattcagctaccgcagaaaactctatgtttttaacaaaaatagcaccatacttacaagtaggttttatgccagaagctcgctccacaataagtttaagtggtccaggagcttatgcgtcagcttactatgatttcataaatttacaagaaaatactatagaaaaaactttaaaagcatcagatttaatagaatttaaattcccagaaaataatctatctcaattgacagaacaagaaataaatagtctatggagctttgatcaagcaagtgcaaaatatcaatttgagaaatatgtaagagattatactggtggatctctttctgaagacaatggggtagactttaataaaaatactgccctcgacaaaaactatttattaaataataaaattccatcaaacaatgtagaagaagctggaagtaaaaattatgttcattatatcatacagttacaaggagatgatataagttatgaagcaacatgcaatttattttctaaaaatcctaaaaatagtattattatacaacgaaatatgaatgaaagtgcaaaaagctactttttaagtgatgatggagaatctattttagaattaaataaatataggatacctgaaagattaaaaaataaggaaaaagtaaaagtaacctttattggacatggtaaagatgaattcaacacaagcgaatttgctagattaagtgtagattcactttccaatgagataagttcatttttagataccataaaattagatatatcacctaaaaatgtagaagtaaacttacttggatgtaatatgtttagttatgattttaatgttgaagaaacttatcctgggaagttgctattaagtattatggacaaaattacttccactttacctgatgtaaataaaaattctattactataggagcaaatcaatatgaagtaagaattaatagtgagggaagaaaagaacttctggctcactcaggtaaatggataaataaagaagaagctattatgagcgatttatctagtaaagaatacattttttttgattctatagataataagctaaaagcaaagtccaagaatattccaggattagcatcaatatcagaagatataaaaacattattacttgatgcaagtgttagtcctgatacaaaatttattttaaataatcttaagcttaatattgaatcttctattggtgattacatttattatgaaaaattagagcctgttaaaaatataattcacaattctatagatgatttaatagatgagttcaatctacttgaaaatgtatctgatgaattatatgaattaaaaaaattaaataatctagatgagaagtatttaatatcttttgaagatatctcaaaaaataattcaacttactctgtaagatttattaacaaaagtaatggtgagtcagtttatgtagaaacagaaaaagaaattttttcaaaatatagcgaacatattacaaaagaaataagtactataaagaatagtataattacagatgttaatggtaatttattggataatatacagttagatcatacttctcaagttaatacattaaacgcagcattctttattcaatcattaatagattatagtagcaataaagatgtactgaatgatttaagtacctcagttaaggttcaactttatgctcaactatttagtacaggtttaaatactatatatgactctatccaattagtaaatttaatatcaaatgcagtaaatgatactataaatgtactacctacaataacagaggggatacctattgtatctactatattagacggaataaacttaggtgcagcaattaaggaattactagacgaacatgacccattactaaaaaaagaattagaagctaaggtgggtgttttagcaataaatatgtcattatctatagctgcaactgtagcttcaattgttggaataggtgctgaagttactattttcttattacctatagctggtatatctgcaggaataccttcattagttaataatgaattaatattgcatgataaggcaacttcagtggtaaactattttaatcatttgtctgaatctaaaaaatatggccctcttaaaacagaagatgataaaattttagttcctattgatgatttagtaatatcagaaatagattttaataataattcgataaaactaggaacatgtaatatattagcaatggaggggggatcaggacacacagtgactggtaatatagatcactttttctcatctccatctataagttctcatattccttcattatcaatttattctgcaataggtatagaaacagaaaatctagatttttcaaaaaaaataatgatgttacctaatgctccttcaagagtgttttggtgggaaactggagcagttccaggtttaagatcattggaaaatgacggaactagattacttgattcaataagagatttatacccaggtaaattttactggagattctatgcttttttcgattatgcaataactacattaaaaccagtttatgaagacactaatattaaaattaaactagataaagatactagaaacttcataatgccaactataactactaacgaaattagaaacaaattatcttattcatttgatggagcaggaggaacttactctttattattatcttcatatccaatatcaacgaatataaatttatctaaagatgatttatggatatttaatattgataatgaagtaagagaaatatctatagaaaatggtactattaaaaaaggaaagttaataaaagatgttttaagtaaaattgatataaataaaaataaacttattataggcaatcaaacaatagatttttcaggcgatatagataataaagatagatatatattcttgacttgtgagttagatgataaaattagtttaataatagaaataaatcttgttgcaaaatcttatagtttgttattgtctggggataaaaattatttgatatccaatttatctaatattattgagaaaatcaatactttaggcctagatagtaaaaatatagcgtacaattacactgatgaatctaataataaatattttggagctatatctaaaacaagtcaaaaaagcataatacattataaaaaagacagtaaaaatatattagaattttataatgacagtacattagaatttaacagtaaagattttattgctgaagatataaatgtatttatgaaagatgatattaatactataacaggaaaatactatgttgataataatactgataaaagtatagatttctctatttctttagttagtaaaaatcaagtaaaagtaaatggattatatttaaatgaatccgtatactcatcttaccttgattttgtgaaaaattcagatggacaccataatacttctaattttatgaatttatttttggacaatataagtttctggaaattgtttgggtttgaaaatataaattttgtaatcgataaatactttacccttgttggtaaaactaatcttggatatgtagaatttatttgtgacaataataaaaatatagatatatattttggtgaatggaaaacatcgtcatctaaaagcactatatttagcggaaatggtagaaatgttgtagtagagcctatatataatcctgatacgggtgaagatatatctacttcactagatttttcctatgaacctctctatggaatagatagatatatcaataaagtattgatagcacctgatttatatacaagtttaataaatattaataccaattattattcaaatgagtactaccctgagattatagttcttaacccaaatacattccacaaaaaagtaaatataaatttagatagttcttcttttgagtataaatggtctacagaaggaagtgactttattttagttagatacttagaagaaagtaataaaaaaatattacaaaaaataagaatcaaaggtatcttatctaatactcaatcatttaataaaatgagtatagattttaaagatattaaaaaactatcattaggatatataatgagtaattttaaatcatttaattctgaaaatgaattagatagagatcatttaggatttaaaataatagataataaaacttattactatgatgaagatagtaaattagttaaaggattaatcaatataaataattcattattctattttgatcctatagaatttaacttagtaactggatggcaaactatcaatggtaaaaaatattattttgatataaatactggagcagctttaattagttataaaattattaatggtaaacacttttattttaataatgatggtgtgatgcagttgggagtatttaaaggacctgatggatttgaatattttgcacctgccaatactcaaaataataacatagaaggtcaggctatagtttatcaaagtaaattcttaactttgaatggcaaaaaatattattttgataatgactcaaaagcagtcactggatggagaattattaacaatgagaaatattactttaatcctaataatgctattgctgcagtcggattgcaagtaattgacaataataagtattatttcaatcctgacactgctatcatctcaaaaggttggcagactgttaatggtagtagatactactttgatactgataccgctattgcctttaatggttataaaactattgatggtaaacacttttattttgatagtgattgtgtagtgaaaataggtgtgtttagtacctctaatggatttgaatattttgcacctgctaatacttataataataacatagaaggtcaggctatagtttatcaaagtaaattcttaactttgaatggtaaaaaatattactttgataataactcaaaagcagttaccggatggcaaactattgatagtaaaaaatattactttaatactaacactgctgaagcagctactggatggcaaactattgatggtaaaaaatattactttaatactaacactgctgaagcagctactggatggcaaactattgatggtaaaaaatattactttaatactaacactgctatagcttcaactggttatacaattattaatggtaaacatttttattttaatactgatggtattatgcagataggagtgtttaaaggacctaatggatttgaatattttgcacctgctaatacggatgctaacaacatagaaggtcaagctatactttaccaaaatgaattcttaactttgaatggtaaaaaatattactttggtagtgactcaaaagcagttactggatggagaattattaacaataagaaatattactttaatcctaataatgctattgctgcaattcatctatgcactataaataatgacaagtattactttagttatgatggaattcttcaaaatggatatattactattgaaagaaataatttctattttgatgctaataatgaatctaaaatggtaacaggagtatttaaaggacctaatggatttgagtattttgcacctgctaatactcacaataataacatagaaggtcaggctatagtttaccagaacaaattcttaactttgaatggcaaaaaatattattttgataatgactcaaaagcagttactggatggcaaaccattgatggtaaaaaatattactttaatcttaacactgctgaagcagctactggatggcaaactattgatggtaaaaaatattactttaatcttaacactgctgaagcagctactggatggcaaactattgatggtaaaaaatattactttaatactaacactttcatagcctcaactggttatacaagtattaatggtaaacatttttattttaatactgatggtattatgcagataggagtgtttaaaggacctaatggatttgaatactttgcacctgctaatactcataataataacatagaaggtcaagctatactttaccaaaataaattcttaactttgaatggtaaaaaatattactttggtagtgactcaaaagcagttaccggattgcgaactattgatggtaaaaaatattactttaatactaacactgctgttgcagttactggatggcaaactattaatggtaaaaaatactactttaatactaacacttctatagcttcaactggttatacaattattagtggtaaacatttttattttaatactgatggtattatgcagataggagtgtttaaaggacctgatggatttgaatactttgcacctgctaatacagatgctaacaatatagaaggtcaagctatacgttatcaaaatagattcctatatttacatgacaatatatattattttggtaataattcaaaagcagctactggttgggtaactattgatggtaatagatattacttcgagcctaatacagctatgggtgcgaatggttataaaactattgataataaaaatttttactttagaaatggtttacctcagataggagtgtttaaagggtctaatggatttgaatactttgcacctgctaatacggatgctaacaatatagaaggtcaagctatacgttatcaaaatagattcctacatttacttggaaaaatatattactttggtaataattcaaaagcagttactggatggcaaactattaatggtaaagtatattactttatgcctgatactgctatggctgcagctggtggacttttcgagattgatggtgttatatatttctttggtgttgatggagtaaaagcccctgggatatatggct aa Amino acid 6MSLISKEELIKLAYSIRPRENEYKTILTNLDEYNKLTTNNNENKYLQ  sequence ofLKKLNESIDVFMNKYKTSSRNRALSNLKKDILKEVILIKNSNTSPVE  trdAKNLHFVWIGGEVSDIALEYIKQWADINAEYNIKLWYDSEAFLVNTLK  (strain 630)KAIVESSTTEALQLLEEEIQNPQFDNMKFYKKRMEFIYDRQKRFINYYKSQINKPTVPTIDDIIKSHLVSEYNRDETVLESYRTNSLRKINSNHGIDIRANSLFTEQELLNIYSQELLNRGNLAAASDIVRLLALKNFGGVYLDVDMLPGIHSDLFKTISRPSSIGLDRWEMIKLEAIMKYKKYINNYTSENFDKLDQQLKDNFKLIIESKSEKSEIFSKLENLNVSDLEIKIAFALGSVINQALISKQGSYLTNLVIEQVKNRYQFLNQHLNPAIESDNNFTDTTKIFHDSLFNSATAENSMFLTKIAPYLQVGFMPEARSTISLSGPGAYASAYYDFINLQENTIEKTLKASDLIEFKFPENNLSQLTEQEINSLWSFDQASAKYQFEKYVRDYTGGSLSEDNGVDFNKNTALDKNYLLNNKIPSNNVEEAGSKNYVHYIIQLQGDDISYEATCNLFSKNPKNSIIIQRNMNESAKSYFLSDDGESILELNKYRIPERLKNKEKVKVTFIGHGKDEFNTSEFARLSVDSLSNEISSFLDTIKLDISPKNVEVNLLGCNMFSYDFNVEETYPGKLLLSIMDKITSTLPDVNKNSITIGANQYEVRINSEGRKELLAHSGKWINKEEAIMSDLSSKEYIFFDSIDNKLKAKSKNIPGLASISEDIKTLLLDASVSPDTKFILNNLKLNIESSIGDYIYYEKLEPVKNIIHNSIDDLIDEFNLLENVSDELYELKKLNNLDEKYLISFEDISKNNSTYSVRFINKSNGESVYVETEKEIFSKYSEHITKEISTIKNSIITDVNGNLLDNIQLDHTSQVNTLNAAFFIQSLIDYSSNKDVLNDLSTSVKVQLYAQLFSTGLNTIYDSIQLVNLISNAVNDTINVLPTITEGIPIVSTILDGINLGAAIKELLDEHDPLLKKELEAKVGVLAINMSLSIAATVASIVGIGAEVTIFLLPIAGISAGIPSLVNNELILHDKATSVVNYFNHLSESKKYGPLKTEDDKILVPIDDLVISEIDFNNNSIKLGTCNILAMEGGSGHTVTGNIDHFFSSPSISSHIPSLSIYSAIGIETENLDFSKKIMMLPNAPSRVFWWETGAVPGLRSLENDGTRLLDSIRDLYPGKFYWRFYAFFDYAITTLKPVYEDTNIKIKLDKDTRNFIMPTITTNEIRNKLSYSFDGAGGTYSLLLSSYPISTNINLSKDDLWIFNIDNEVREISIENGTIKKGKLIKDVLSKIDINKNKLIIGNQTIDFSGDIDNKDRYIFLTCELDDKISLIIEINLVAKSYSLLLSGDKNYLISNLSNIIEKINTLGLDSKNIAYNYTDESNNKYFGAISKTSQKSIIHYKKDSKNILEFYNDSTLEFNSKDFIAEDINVFMKDDINTITGKYYVDNNTDKSIDFSISLVSKNQVKVNGLYLNESVYSSYLDFVKNSDGHHNTSNFMNLFLDNISFWKLFGFENINFVIDKYFTLVGKTNLGYVEFICDNNKNIDIYFGEWKTSSSKSTIFSGNGRNVVVEPIYNPDTGEDISTSLDFSYEPLYGIDRYINKVLIAPDLYTSLININTNYYSNEYYPEIIVLNPNTFHKKVNINLDSSSFEYKWSTEGSDFILVRYLEESNKKILQKIRIKGILSNTQSFNKMSIDFKDIKKLSLGYIMSNFKSFNSENELDRDHLGFKIIDNKTYYYDEDSKLVKGLININNSLFYFDPIEFNLVTGWQTINGKKYYFDINTGAALISYKIINGKHFYFNNDGVMQLGVFKGPDGFEYFAPANTQNNNIEGQAIVYQSKFLTLNGKKYYFDNDSKAVTGWRIINNEKYYFNPNNAIAAVGLQVIDNNKYYFNPDTAIISKGWQTVNGSRYYFDTDTAIAFNGYKTIDGKHFYFDSDCVVKIGVFSTSNGFEYFAPANTYNNNIEGQAIVYQSKFLTLNGKKYYFDNNSKAVTGWQTIDSKKYYFNTNTAEAATGWQTIDGKKYYFNTNTAEAATGWQTIDGKKYYFNTNTAIASTGYTIINGKHFYFNTDGIMQIGVFKGPNGFEYFAPANTDANNIEGQAILYQNEFLTLNGKKYYFGSDSKAVTGWRIINNKKYYFNPNNAIAAIHLCTINNDKYYFSYDGILQNGYITIERNNFYFDANNESKMVTGVFKGPNGFEYFAPANTHNNNIEGQAIVYQNKFLTLNGKKYYFDNDSKAVTGWQTIDGKKYYFNLNTAEAATGWQTIDGKKYYFNLNTAEAATGWQTIDGKKYYFNTNTFIASTGYTSINGKHFYFNTDGIMQIGVFKGPNGFEYFAPANTHNNNIEGQAILYQNKFLTLNGKKYYFGSDSKAVTGLRTIDGKKYYFNTNTAVAVTGWQTINGKKYYFNTNTSIASTGYTIISGKHFYFNTDGIMQIGVFKGPDGFEYFAPANTDANNIEGQAIRYQNRFLYLHDNIYYFGNNSKAATGWVTIDGNRYYFEPNTAMGANGYKTIDNKNFYFRNGLPQIGVFKGSNGFEYFAPANTDANNIEGQAIRYQNRFLHLLGKIYYFGNNSKAVTGWQTINGKVYYFMPDTAMAAAGGLFEIDGVIYFFGVDGVKAPGIYG Nucleic acid 7atgagtttagttaatagaaaacagttagaaaaaatggcaaatgtaag  sequence ofatttcgtactcaagaagatgaatatgttgcaatattggatgctttag  trdBaagaatatcataatatgtcagagaatactgtagtcgaaaaatattta  (strain 630)aaattaaaagatataaatagtttaacagatatttatatagatacatataaaaaatctggtagaaataaagccttaaaaaaatttaaggaatatctagttacagaagtattagagctaaagaataataatttaactccagttgagaaaaatttacattttgtttggattggaggtcaaataaatgacactgctattaattatataaatcaatggaaagatgtaaatagtgattataatgttaatgttttttatgatagtaatgcatttttgataaacacattgaaaaaaactgtagtagaatcagcaataaatgatacacttgaatcatttagagaaaacttaaatgaccctagatttgactataataaattcttcagaaaacgtatggaaataatttatgataaacagaaaaatttcataaactactataaagctcaaagagaagaaaatcctgaacttataattgatgatattgtaaagacatatctttcaaatgagtattcaaaggagatagatgaacttaatacctatattgaagaatccttaaataaaattacacagaatagtggaaatgatgttagaaactttgaagaatttaaaaatggagagtcattcaacttatatgaacaagagttggtagaaaggtggaatttagctgctgcttctgacatattaagaatatctgcattaaaagaaattggtggtatgtatttagatgttgatatgttaccaggaatacaaccagacttatttgagtctatagagaaacctagttcagtaacagtggatttttgggaaatgacaaagttagaagctataatgaaatacaaagaatatataccagaatatacctcagaacattttgacatgttagacgaagaagttcaaagtagttttgaatctgttctagcttctaagtcagataaatcagaaatattctcatcacttggtgatatggaggcatcaccactagaagttaaaattgcatttaatagtaagggtattataaatcaagggctaatttctgtgaaagactcatattgtagcaatttaatagtaaaacaaatcgagaatagatataaaatattgaataatagtttaaatccagctattagcgaggataatgattttaatactacaacgaatacctttattgatagtataatggctgaagctaatgcagataatggtagatttatgatggaactaggaaagtatttaagagttggtttcttcccagatgttaaaactactattaacttaagtggccctgaagcatatgcggcagcttatcaagatttattaatgtttaaagaaggcagtatgaatatccatttgatagaagctgatttaagaaactttgaaatctctaaaactaatatttctcaatcaactgaacaagaaatggctagcttatggtcatttgacgatgcaagagctaaagctcaatttgaagaatataaaaggaattattttgaaggttctcttggtgaagatgataatcttgatttttctcaaaatatagtagttgacaaggagtatcttttagaaaaaatatcttcattagcaagaagttcagagagaggatatatacactatattgttcagttacaaggagataaaattagttatgaagcagcatgtaacttatttgcaaagactccttatgatagtgtactgtttcagaaaaatatagaagattcagaaattgcatattattataatcctggagatggtgaaatacaagaaatagacaagtataaaattccaagtataatttctgatagacctaagattaaattaacatttattggtcatggtaaagatgaatttaatactgatatatttgcaggttttgatgtagattcattatccacagaaatagaagcagcaatagatttagctaaagaggatatttctcctaagtcaatagaaataaatttattaggatgtaatatgtttagctactctatcaacgtagaggagacttatcctggaaaattattacttaaagttaaagataaaatatcagaattaatgccatctataagtcaagactctattatagtaagtgcaaatcaatatgaagttagaataaatagtgaaggaagaagagaattattggatcattctggtgaatggataaataaagaagaaagtattataaaggatatttcatcaaaagaatatatatcatttaatcctaaagaaaataaaattacagtaaaatctaaaaatttacctgagctatctacattattacaagaaattagaaataattctaattcaagtgatattgaactagaagaaaaagtaatgttaacagaatgtgagataaatgttatttcaaatatagatacgcaaattgttgaggaaaggattgaagaagctaagaatttaacttctgactctattaattatataaaagatgaatttaaactaatagaatctatttctgatgcactatgtgacttaaaacaacagaatgaattagaagattctcattttatatcttttgaggacatatcagagactgatgagggatttagtataagatttattaataaagaaactggagaatctatatttgtagaaactgaaaaaacaatattctctgaatatgctaatcatataactgaagagatttctaagataaaaggtactatatttgatactgtaaatggtaagttagtaaaaaaagtaaatttagatactacacacgaagtaaatactttaaatgctgcattttttatacaatcattaatagaatataatagttctaaagaatctcttagtaatttaagtgtagcaatgaaagtccaagtttacgctcaattatttagtactggtttaaatactattacagatgcagccaaagttgttgaattagtatcaactgcattagatgaaactatagacttacttcctacattatctgaaggattacctataattgcaactattatagatggtgtaagtttaggtgcagcaatcaaagagctaagtgaaacgagtgacccattattaagacaagaaatagaagctaagataggtataatggcagtaaatttaacaacagctacaactgcaatcattacttcatctttggggatagctagtggatttagtatacttttagttcctttagcaggaatttcagcaggtataccaagcttagtaaacaatgaacttgtacttcgagataaggcaacaaaggttgtagattattttaaacatgtttcattagttgaaactgaaggagtatttactttattagatgataaaataatgatgccacaagatgatttagtgatatcagaaatagattttaataataattcaatagttttaggtaaatgtgaaatctggagaatggaaggtggttcaggtcatactgtaactgatgatatagatcacttcttttcagcaccatcaataacatatagagagccacacttatctatatatgacgtattggaagtacaaaaagaagaacttgatttgtcaaaagatttaatggtattacctaatgctccaaatagagtatttgcttgggaaacaggatggacaccaggtttaagaagcttagaaaatgatggcacaaaactgttagaccgtataagagataactatgaaggtgagttttattggagatattttgcttttatagctgatgctttaataacaacattaaaaccaagatatgaagatactaatataagaataaatttagatagtaatactagaagttttatagttccaataataactacagaatatataagagaaaaattatcatattctttctatggttcaggaggaacttatgcattgtctctttctcaatataatatgggtataaatatagaattaagtgaaagtgatgtttggattatagatgttgataatgttgtgagagatgtaactatagaatctgataaaattaaaaaaggtgatttaatagaaggtattttatctacactaagtattgaagagaataaaattatcttaaatagccatgagattaatttttctggtgaggtaaatggaagtaatggatttgtttctttaacattttcaattttagaaggaataaatgcaattatagaagttgatttattatctaaatcatataaattacttatttctggcgaattaaaaatattgatgttaaattcaaatcatattcaacagaaaatagattatataggattcaatagcgaattacagaaaaatataccatatagctttgtagatagtgaaggaaaagagaatggttttattaatggttcaacaaaagaaggtttatttgtatctgaattacctgatgtagttcttataagtaaggtttatatggatgatagtaagccttcatttggatattatagtaataatttgaaagatgtcaaagttataactaaagataatgttaatatattaacaggttattatcttaaggatgatataaaaatctctctttctttgactctacaagatgaaaaaactataaagttaaatagtgtgcatttagatgaaagtggagtagctgagattttgaagttcatgaatagaaaaggtaatacaaatacttcagattctttaatgagctttttagaaagtatgaatataaaaagtattttcgttaatttcttacaatctaatattaagtttatattagatgctaattttataataagtggtactacttctattggccaatttgagtttatttgtgatgaaaatgataatatacaaccatatttcattaagtttaatacactagaaactaattatactttatatgtaggaaatagacaaaatatgatagtggaaccaaattatgatttagatgattctggagatatatcttcaactgttatcaatttctctcaaaagtatctttatggaatagacagttgtgttaataaagttgtaatttcaccaaatatttatacagatgaaataaatataacgcctgtatatgaaacaaataatacttatccagaagttattgtattagatgcaaattatataaatgaaaaaataaatgttaatatcaatgatctatctatacgatatgtatggagtaatgatggtaatgattttattcttatgtcaactagtgaagaaaataaggtgtcacaagttaaaataagattcgttaatgtttttaaagataagactttggcaaataagctatcttttaactttagtgataaacaagatgtacctgtaagtgaaataatcttatcatttacaccttcatattatgaggatggattgattggctatgatttgggtctagtttctttatataatgagaaattttatattaataactttggaatgatggtatctggattaatatatattaatgattcattatattattttaaaccaccagtaaataatttgataactggatttgtgactgtaggcgatgataaatactactttaatccaattaatggtggagctgcttcaattggagagacaataattgatgacaaaaattattatttcaaccaaagtggagtgttacaaacaggtgtatttagtacagaagatggatttaaatattttgccccagctaatacacttgatgaaaacctagaaggagaagcaattgattttactggaaaattaattattgacgaaaatatttattattttgatgataattatagaggagctgtagaatggaaagaattagatggtgaaatgcactattttagcccagaaacaggtaaagcttttaaaggtctaaatcaaataggtgattataaatactatttcaattctgatggagttatgcaaaaaggatttgttagtataaatgataataaacactattttgatgattctggtgttatgaaagtaggttacactgaaatagatggcaagcatttctactttgctgaaaacggagaaatgcaaataggagtatttaatacagaagatggatttaaatattttgctcatcataatgaagatttaggaaatgaagaaggtgaagaaatctcatattctggtatattaaatttcaataataaaatttactattttgatgattcatttacagctgtagttggatggaaagatttagaggatggttcaaagtattattttgatgaagatacagcagaagcatatataggtttgtcattaataaatgatggtcaatattattttaatgatgatggaattatgcaagttggatttgtcactataaatgataaagtcttctacttctctgactctggaattatagaatctggagtacaaaacatagatgacaattatttctatatagatgataatggtatagttcaaattggtgtatttgatacttcagatggatataaatattttgcacctgctaatactgtaaatgataatatttacggacaagcagttgaatatagtggtttagttagagttggtgaagatgtatattattttggagaaacatatacaattgagactggatggatatatgatatggaaaatgaaagtgataaatattatttcaatccagaaactaaaaaagcatgcaaaggtattaatttaattgatgatataaaatattattttgatgagaagggcataatgagaacgggtcttatatcatttgaaaataataattattactttaatgagaatggtgaaatgcaatttggttatataaatatagaagataagatgttctattttggtgaagatggtgtcatgcagattggagtatttaatacaccagatggatttaaatactttgcacatcaaaatactttggatgagaattttgagggagaatcaataaactatactggttggttagatttagatgaaaagagatattattttacagatgaatatattgcagcaactggttcagttattattgatggtgaggagtattattttgatcctgatacagctcaattagtgattagtga atag Amino acid 8MSLVNRKQLEKMANVRFRTQEDEYVAILDALEEYHNMSENTVVEKYL  sequence ofKLKDINSLTDIYIDTYKKSGRNKALKKFKEYLVTEVLELKNNNLTPV  trdBEKNLHFVWIGGQINDTAINYINQWKDVNSDYNVNVFYDSNAFLINTL  (strain 630)KKTVVESAINDTLESFRENLNDPRFDYNKFFRKRMEIIYDKQKNFINYYKAQREENPELIIDDIVKTYLSNEYSKEIDELNTYIEESLNKITQNSGNDVRNFEEFKNGESFNLYEQELVERWNLAAASDILRISALKEIGGMYLDVDMLPGIQPDLFESIEKPSSVTVDFWEMTKLEAIMKYKEYIPEYTSEHFDMLDEEVQSSFESVLASKSDKSEIFSSLGDMEASPLEVKIAFNSKGIINQGLISVKDSYCSNLIVKQIENRYKILNNSLNPAISEDNDFNTTTNTFIDSIMAEANADNGRFMMELGKYLRVGFFPDVKTTINLSGPEAYAAAYQDLLMFKEGSMNIHLIEADLRNFEISKTNISQSTEQEMASLWSFDDARAKAQFEEYKRNYFEGSLGEDDNLDFSQNIVVDKEYLLEKISSLARSSERGYIHYIVQLQGDKISYEAACNLFAKTPYDSVLFQKNIEDSEIAYYYNPGDGEIQEIDKYKIPSIISDRPKIKLTFIGHGKDEFNTDIFAGFDVDSLSTEIEAAIDLAKEDISPKSIEINLLGCNMFSYSINVEETYPGKLLLKVKDKISELMPSISQDSIIVSANQYEVRINSEGRRELLDHSGEWINKEESIIKDISSKEYISFNPKENKITVKSKNLPELSTLLQEIRNNSNSSDIELEEKVMLTECEINVISNIDTQIVEERIEEAKNLTSDSINYIKDEFKLIESISDALCDLKQQNELEDSHFISFEDISETDEGFSIRFINKETGESIFVETEKTIFSEYANHITEEISKIKGTIFDTVNGKLVKKVNLDTTHEVNTLNAAFFIQSLIEYNSSKESLSNLSVAMKVQVYAQLFSTGLNTITDAAKVVELVSTALDETIDLLPTLSEGLPIIATIIDGVSLGAAIKELSETSDPLLRQEIEAKIGIMAVNLTTATTAIITSSLGIASGFSILLVPLAGISAGIPSLVNNELVLRDKATKVVDYFKHVSLVETEGVFTLLDDKIMMPQDDLVISEIDFNNNSIVLGKCEIWRMEGGSGHTVTDDIDHFFSAPSITYREPHLSIYDVLEVQKEELDLSKDLMVLPNAPNRVFAWETGWTPGLRSLENDGTKLLDRIRDNYEGEFYWRYFAFIADALITTLKPRYEDTNIRINLDSNTRSFIVPIITTEYIREKLSYSFYGSGGTYALSLSQYNMGINIELSESDVWIIDVDNVVRDVTIESDKIKKGDLIEGILSTLSIEENKIILNSHEINFSGEVNGSNGFVSLTFSILEGINAIIEVDLLSKSYKLLISGELKILMLNSNHIQQKIDYIGFNSELQKNIPYSFVDSEGKENGFINGSTKEGLFVSELPDVVLISKVYMDDSKPSFGYYSNNLKDVKVITKDNVNILTGYYLKDDIKISLSLTLQDEKTIKLNSVHLDESGVAEILKFMNRKGNTNTSDSLMSFLESMNIKSIFVNFLQSNIKFILDANFIISGTTSIGQFEFICDENDNIQPYFIKFNTLETNYTLYVGNRQNMIVEPNYDLDDSGDISSTVINFSQKYLYGIDSCVNKVVISPNIYTDEINITPVYETNNTYPEVIVLDANYINEKINVNINDLSIRYVWSNDGNDFILMSTSEENKVSQVKIRFVNVFKDKTLANKLSFNFSDKQDVPVSEIILSFTPSYYEDGLIGYDLGLVSLYNEKFYINNFGMMVSGLIYINDSLYYFKPPVNNLITGFVTVGDDKYYFNPINGGAASIGETIIDDKNYYFNQSGVLQTGVFSTEDGFKYFAPANTLDENLEGEAIDFTGKLIIDENIYYFDDNYRGAVEWKELDGEMHYFSPETGKAFKGLNQIGDYKYYFNSDGVMQKGFVSINDNKHYFDDSGVMKVGYTEIDGKHFYFAENGEMQIGVFNTEDGFKYFAHHNEDLGNEEGEEISYSGILNFNNKIYYFDDSFTAVVGWKDLEDGSKYYFDEDTAEAYIGLSLINDGQYYFNDDGIMQVGFVTINDKVFYFSDSGIIESGVQNIDDNYFYIDDNGIVQIGVFDTSDGYKYFAPANTVNDNIYGQAVEYSGLVRVGEDVYYFGETYTIETGWIYDMENESDKYYFNPETKKACKGINLIDDIKYYFDEKGIMRTGLISFENNNYYFNENGEMQFGYINIEDKMFYFGEDGVMQIGVFNTPDGFKYFAHQNTLDENFEGESINYTGWLDLDEKRYYFTDEYIAATGSVIIDG EEYYFDPDTAQLVISEForward primer 9 caccACTAGTatgaacttagtaactggatggc Reverse primer 10CTCGAGttagccatatatcccaggggc Forward primer 11caccATGCATatgagtttagttaatagaaaacag Reverse primer 12ggcCTCGAGctattcactaatcactaattgagc Forward primer 13AGATCTATGCATGAGCTCctcgagcccaaaacgaaaggctcagc Reverse primer 14cggtccggggccatatatcccaggggcttttactcc Forward primer 15caccCCATTGatggtaacaggagtatttaaagga Reverse primer 16CTCGAGctattcactaatcactaattgagctg C-TADCTB 17atggtaacaggagtatttaaaggacctaatggatttgagtattttgc  (nucleic acidacctgctaatactcacaataataacatagaaggtcaggctatagttt  sequence)accagaacaaattcttaactttgaatggcaaaaaatattattttgat aatgactcaaaagcagttactggatggcaaaccattgatggtaaaaaatattactttaatcttaacactgctgaagcagctactggatggcaaactattgatggtaaaaaatattactttaatcttaacactgctgaagcagctactggatggcaaactattgatggtaaaaaatattactttaatactaacactttcatagcctcaactggttatacaagtattaatggtaaacatttttattttaatactgatggtattatgcagataggagtgtttaaaggacctaatggatttgaatactttgcacctgctaatacggatgctaacaacatagaaggtcaagctatactttaccaaaataaattcttaactttgaatggtaaaaaatattactttggtagtgactcaaaagcagttaccggactgcgaactattgatggtaaaaaatattactttaatactaacactgctgttgcagttactggatggcaaactattaatggtaaaaaatactactttaatactaacacttctatagcttcaactggttatacaattattagtggtaaacatttttattttaatactgatggtattatgcagataggagtgtttaaaggacctgatggatttgaatactttgcacctgctaatacagatgctaacaatatagaaggtcaagctatacgttatcaaaatagattcctatatttacatgacaatatatattattttggtaataattcaaaagcggctactggttgggtaactattgatggtaatagatattacttcgagcctaatacagctatgggtgcgaatggttataaaactattgataataaaaatttttactttagaaatggtttacctcagataggagtgtttaaagggtctaatggatttgaatactttgcacctgctaatacggatgctaacaatatagaaggtcaagctatacgttatcaaaatagattcctacatttacttggaaaaatatattactttggtaataattcaaaagcagttactggatggcaaactattaatggtaaagtatattactttatgcctgatactgctatggctgcagctggtggacttttcgagattgatggtgttatatatttctttggtgttgatggagtaaaagcccctgggatatatggcAGATCTATGCATaatttgataactggatttgtgactgtaggcgatgataaatactactttaatccaattaatggtggagctgcttcaattggagagacaataattgatgacaaaaattattatttcaaccaaagtggagtgttacaaacaggtgtatttagtacagaagatggatttaaatattttgccccagctaatacacttgatgaaaacctagaaggagaagcaattgattttactggaaaattaattattgacgaaaatatttattattttgatgataattatagaggagctgtagaatggaaagaattagatggtgaaatgcactattttagcccagaaacaggtaaagcttttaaaggtctaaatcaaataggtgattataaatactatttcaattctgatggagttatgcaaaaaggatttgttagtataaatgataataaacactattttgatgattctggtgttatgaaagtaggttacactgaaatagatggcaagcatttctactttgctgaaaacggagaaatgcaaataggagtatttaatacagaagatggatttaaatattttgctcatcataatgaagatttaggaaatgaagaaggtgaagaaatctcatattctggtatattaaatttcaataataaaatttactattttgatgattcatttacagctgtagttggatggaaagatttagaggatggttcaaagtattattttgatgaagatacagcagaagcatatataggtttgtcattaataaatgatggtcaatattattttaatgatgatggaattatgcaagttggatttgtcactataaatgataaagtcttctacttctctgactctggaattatagaatctggagtacaaaacatagatgacaattatttctatatagatgataatggtatagttcaaattggtgtatttgatacttcagatggatataaatattttgcacctgctaatactgtaaatgataatatttacggacaagcagttgaatatagtggtttagttagagttggggaagatgtatattattttggagaaacatatacaattgagactggatggatatatgatatggaaaatgaaagtgataaatattatttcaatccagaaactaaaaaagcatgcaaaggtattaatttaattgatgatataaaatattattttgatgagaagggcataatgagaacgggtcttatatcatttgaaaataataattattactttaatgagaatggtgaaatgcaatttggttatataaatatagaagataagatgttctattttggtgaagatggtgtcatgcagattggagtatttaatacaccagatggatttaaatactttgcacatcaaaatactttggatgagaattttgagggagaatcaataaactatactggttggttagatttagatgaaaagagatattattttacagatgaatatattgcagcaactggttcagttattattgatggtgaggagtattattttgatcctgatacagctcaattagtgattagtgaaCTCGAGggattaatatatattaatgattcattatattattttaaaccaccagtaaataatttgataactggatttgtgactgtaggcgatgataaatactactttaatccaattaatggtggagctgcttcaattggagagacaataattgatgacaaaaattattatttcaaccaaagtggagtgttacaaacaggtgtatttagtacagaagatggatttaaatattttgccccagctaatacacttgatgaaaacctagaaggagaagcaattgattttactggaaaattaattattgacgaaaatatttattattttgatgataattatagaggagctgtagaatggaaagaattagatggtgaaatgcactattttagcccagaaacaggtaaagcttttaaaggtctaaatcaaataggtgattataaatactatttcaattctgatggagttatgcaaaaaggatttgttagtataaatgataataaacactattttgatgattctggtgttatgaaagtaggttacactgaaatagatggcaagcatttctactttgctgaaaacggagaaatgcaaataggagtatttaatacagaagatggatttaaatattttgctcatcataatgaagatttaggaaatgaagaaggtgaagaaatctcatattctggtatattaaatttcaataataaaatttactattttgatgattcatttacagctgtagttggatggaaagatttagaggatggttcaaagtattattttgatgaagatacagcagaagcatatataggtttgtcattaataaatgatggtcaatattattttaatgatgatggaattatgcaagttggatttgtcactataaatgataaagtcttctacttctctgactctggaattatagaatctggagtacaaaacatagatgacaattatttctatatagatgataatggtatagttcaaattggtgtatttgatacttcagatggatataaatattttgcacctgctaatactgtaaatgataatatttacggacaagcagttgaatatagtggtttagttagagttggggaagatgtatattattttggagaaacatatacaattgagactggatggatatatgatatggaaaatgaaagtgataaatattatttcaatccagaaactaaaaaagcatgcaaaggtattaatttaattgatgatataaaatattattttgatgagaagggcataatgagaacgggtcttatatcatttgaaaataataattattactttaatgagaatggtgaaatgcaatttggttatataaatatagaagataagatgttctattttggtgaagatggtgtcatgcagattggagtatttaatacaccagatggatttaaatactttgcacatcaaaatactttggatgagaattttgagggagaatcaataaactatactggttggttagatttagatgaaaagagatattattttacagatgaatatattgcagcaactggttcagttattattgatggtgaggagtattattttgatcctgatacagctcaat tagtgattagtgaatagC-TADCTB 18 MVTGVFKGPNGFEYFAPANTHNNNIEGQAIVYQNKFLTLNGKKYYFD  (amino acidNDSKAVTGWQTIDGKKYYFNLNTAEAATGWQTIDGKKYYFNLNTAEA  sequence)ATGWQTIDGKKYYFNTNTFIASTGYTSINGKHFYFNTDGIMQIGVFK GPNGFEYFAPANTDANNIEGQAILYQNKFLTLNGKKYYFGSDSKAVTGLRTIDGKKYYFNTNTAVAVTGWQTINGKKYYFNTNTSIASTGYTIISGKHFYFNTDGIMQIGVFKGPDGFEYFAPANTDANNIEGQAIRYQNRFLYLHDNIYYFGNNSKAATGWVTIDGNRYYFEPNTAMGANGYKTIDNKNFYFRNGLPQIGVFKGSNGFEYFAPANTDANNIEGQAIRYQNRFLHLLGKIYYFGNNSKAVTGWQTINGKVYYFMPDTAMAAAGGLFEIDGVIYFFGVDGVKAPGIYGRSMHNLITGFVTVGDDKYYFNPINGGAASIGETIIDDKNYYFNQSGVLQTGVFSTEDGFKYFAPANTLDENLEGEAIDFTGKLIIDENIYYFDDNYRGAVEWKELDGEMHYFSPETGKAFKGLNQIGDYKYYFNSDGVMQKGFVSINDNKHYFDDSGVMKVGYTEIDGKHFYFAENGEMQIGVFNTEDGFKYFAHHNEDLGNEEGEEISYSGILNFNNKIYYFDDSFTAVVGWKDLEDGSKYYFDEDTAEAYIGLSLINDGQYYFNDDGIMQVGFVTINDKVFYFSDSGIIESGVQNIDDNYFYIDDNGIVQIGVFDTSDGYKYFAPANTVNDNIYGQAVEYSGLVRVGEDVYYFGETYTIETGWIYDMENESDKYYFNPETKKACKGINLIDDIKYYFDEKGIMRTGLISFENNNYYFNENGEMQFGYINIEDKMFYFGEDGVMQIGVFNTPDGFKYFAHQNTLDENFEGESINYTGWLDLDEKRYYFTDEYIAATGSVIIDGEEYYFDPDTAQLVISELEGLIYINDSLYYFKPPVNNLITGFVTVGDDKYYFNPINGGAASIGETIIDDKNYYFNQSGVLQTGVFSTEDGFKYFAPANTLDENLEGEAIDFTGKLIIDENIYYFDDNYRGAVEWKELDGEMHYFSPETGKAFKGLNQIGDYKYYFNSDGVMQKGFVSINDNKHYFDDSGVMKVGYTEIDGKHFYFAENGEMQIGVFNTEDGFKYFAHHNEDLGNEEGEEISYSGILNFNNKIYYFDDSFTAVVGWKDLEDGSKYYFDEDTAEAYIGLSLINDGQYYFNDDGIMQVGFVTINDKVFYFSDSGIIESGVQNIDDNYFYIDDNGIVQIGVFDTSDGYKYFAPANTVNDNIYGQAVEYSGLVRVGEDVYYFGETYTIETGWIYDMENESDKYYFNPETKKACKGINLIDDIKYYFDEKGIMRTGLISFENNNYYFNENGEMQFGYINIEDKMFYFGEDGVMQIGVFNTPDGFKYFAHQNTLDENFEGESINYTGWLDLDEKRYYFTDEYIAATGSVIIDGEEYYFDPDTAQLVISE C-TANCTB 19atggtaacaggagtatttaaaggacctaatggatttgagtattttgc  (nucleic acidacctgctaatactcacaataataacatagaaggtcaggctatagttt  sequence)accagaacaaattcttaactttgaatggcaaaaaatattattttgat aatgactcaaaagcagttactggatggcaaaccattgatggtaaaaaatattactttaatcttaacactgctgaagcagctactggatggcaaactattgatggtaaaaaatattactttaatcttaacactgctgaagcagctactggatggcaaactattgatggtaaaaaatattactttaatactaacactttcatagcctcaactggttatacaagtattaatggtaaacatttttattttaatactgatggtattatgcagataggagtgtttaaaggacctaatggatttgaatactttgcacctgctaatacggatgctaacaacatagaaggtcaagctatactttaccaaaataaattcttaactttgaatggtaaaaaatattactttggtagtgactcaaaagcagttaccggactgcgaactattgatggtaaaaaatattactttaatactaacactgctgttgcagttactggatggcaaactattaatggtaaaaaatactactttaatactaacacttctatagcttcaactggttatacaattattagtggtaaacatttttattttaatactgatggtattatgcagataggagtgtttaaaggacctgatggatttgaatactttgcacctgctaatacagatgctaacaatatagaaggtcaagctatacgttatcaaaatagattcctatatttacatgacaatatatattattttggtaataattcaaaagcggctactggttgggtaactattgatggtaatagatattacttcgagcctaatacagctatgggtgcgaatggttataaaactattgataataaaaatttttactttagaaatggtttacctcagataggagtgtttaaagggtctaatggatttgaatactttgcacctgctaatacggatgctaacaatatagaaggtcaagctatacgttatcaaaatagattcctacatttacttggaaaaatatattactttggtaataattcaaaagcagttactggatggcaaactattaatggtaaagtatattactttatgcctgatactgctatggctgcagctggtggacttttcgagattgatggtgttatatatttctttggtgttgatggagtaaaagcccctgggatatatggcAGATCTATGCATaatttgataactggatttgtgactgtaggcgatgataaatactactttaatccaattaatggtggagctgcttcaattggagagacaataattgatgacaaaaattattatttcaaccaaagtggagtgttacaaacaggtgtatttagtacagaagatggatttaaatattttgccccagctaatacacttgatgaaaacctagaaggagaagcaattgattttactggaaaattaattattgacgaaaatatttattattttgatgataattatagaggagctgtagaatggaaagaattagatggtgaaatgcactattttagcccagaaacaggtaaagcttttaaaggtctaaatcaaataggtgattataaatactatttcaattctgatggagttatgcaaaaaggatttgttagtataaatgataataaacactattttgatgattctggtgttatgaaagtaggttacactgaaatagatggcaagcatttctactttgctgaaaacggagaaatgcaaataggagtatttaatacagaagatggatttaaatattttgctcatcataatgaagatttaggaaatgaagaaggtgaagaaatctcatattctggtatattaaatttcaataataaaatttactattttgatgattcatttacagctgtagttggatggaaagatttagaggatggttcaaagtattattttgatgaagatacagcagaagcatatataggtttgtcattaataaatgatggtcaatattattttaatgatgatggaattatgcaagttggatttgtcactataaatgataaagtcttctacttctctgactctggaattatagaatctggagtacaaaacatagatgacaattatttctatatagatgataatggtatagttcaaattggtgtatttgatacttcagatggatataaatattttgcacctgctaatactgtaaatgataatatttacggacaagcagttgaatatagtggtttagttagagttggggaagatgtatattattttggagaaacatatacaattgagactggatggatatatgatatggaaaatgaaagtgataaatattatttcaatccagaaactaaaaaagcatgcaaaggtattaatttaattgatgatataaaatattattttgatgagaagggcataatgagaacgggtcttatatcatttgaaaataataattattactttaatgagaatggtgaaatgcaatttggttatataaatatagaagataagatgttctattttggtgaagatggtgtcatgcagattggagtatttaatacaccagatggatttaaatactttgcacatcaaaatactttggatgagaattttgagggagaatcaataaactatactggttggttagatttagatgaaaagagatattattttacagatgaatatattgcagcaactggttcagttattattgatggtgaggagtattattttgatcctgatacagctcaattagtgattagtgaaCTCGAGggattaatatatattaatgattcattatattattttaaaccaccagtaaataatttgataactggatttgtgactgtaggcgatgataaatactactttaatccaattaatggtggagctgcttcaattggagagacaataattgatgacaaaaattattatttcaaccaaagtggagtgttacaaacaggtgtatttagtacagaagatggatttaaatattttgccccagctaatacacttgatgaaaacctagaaggagaagcaattgattttactggaaaattaattattgacgaaaatatttattattttgatgataattatagaggagctgtagaatggaaagaattagatggtgaaatgcactattttagcccagaaacaggtaaagcttttaaaggtctaaatcaaataggtgattataaatactatttcaattctgatggagttatgcaaaaaggatttgttagtataaatgataataaacactattttgatgattctggtgttatgaaagtaggttacactgaaatagatggcaagcatttctactttgctgaaaacggagaaatgcaaataggagtatttaatacagaagatggatttaaatattttgctcatcataatgaagatttaggaaatgaagaaggtgaagaaatctcatattct C-TANCTB 20MVTGVFKGPNGFEYFAPANTHNNNIEGQAIVYQNKFLTLNGKKYYFD  (amino acidNDSKAVTGWQTIDGKKYYFNLNTAEAATGWQTIDGKKYYFNLNTAEA  sequence)ATGWQTIDGKKYYFNTNTFIASTGYTSINGKHFYFNTDGIMQIGVFK GPNGFEYFAPANTDANNIEGQAILYQNKFLTLNGKKYYFGSDSKAVTGLRTIDGKKYYFNTNTAVAVTGWQTINGKKYYFNTNTSIASTGYTIISGKHFYFNTDGIMQIGVFKGPDGFEYFAPANTDANNIEGQAIRYQNRFLYLHDNIYYFGNNSKAATGWVTIDGNRYYFEPNTAMGANGYKTIDNKNFYFRNGLPQIGVFKGSNGFEYFAPANTDANNIEGQAIRYQNRFLHLLGKIYYFGNNSKAVTGWQTINGKVYYFMPDTAMAAAGGLFEIDGVIYFFGVDGVKAPGIYGRSMHNLITGFVTVGDDKYYFNPINGGAASIGETIIDDKNYYFNQSGVLQTGVFSTEDGFKYFAPANTLDENLEGEAIDFTGKLIIDENIYYFDDNYRGAVEWKELDGEMHYFSPETGKAFKGLNQIGDYKYYFNSDGVMQKGFVSINDNKHYFDDSGVMKVGYTEIDGKHFYFAENGEMQIGVFNTEDGFKYFAHHNEDLGNEEGEEISYSGILNFNNKIYYFDDSFTAVVGWKDLEDGSKYYFDEDTAEAYIGLSLINDGQYYFNDDGIMQVGFVTINDKVFYFSDSGIIESGVQNIDDNYFYIDDNGIVQIGVFDTSDGYKYFAPANTVNDNIYGQAVEYSGLVRVGEDVYYFGETYTIETGWIYDMENESDKYYFNPETKKACKGINLIDDIKYYFDEKGIMRTGLISFENNNYYFNENGEMQFGYINIEDKMFYFGEDGVMQIGVFNTPDGFKYFAHQNTLDENFEGESINYTGWLDLDEKRYYFTDEYIAATGSVIIDGEEYYFDPDTAQLVISELEGLIYINDSLYYFKPPVNNLITGFVTVGDDKYYFNPINGGAASIGETIIDDKNYYFNQSGVLQTGVFSTEDGFKYFAPANTLDENLEGEAIDFTGKLIIDENIYYFDDNYRGAVEWKELDGEMHYFSPETGKAFKGLNQIGDYKYYFNSDGVMQKGFVSINDNKHYFDDSGVMKVGYTEIDGKHFYFAENGEMQIGVFNTEDGFKYFAHHNEDLGN EEGEEISYSPreferred Aspects:Preferred Polypeptides and Uses Thereof:

1. An isolated polypeptide comprising an amino acid sequence having atleast 85%, more preferably at least 90%, even more preferably at least95%, most preferred 99% sequence identity to the amino acid sequence asset forth in SEQ ID NO: 2.

2. An isolated polypeptide comprising an amino acid sequence having atleast 85%, more preferably at least 90%, even more preferably at least95%, most preferred 99% sequence identity to the amino acid sequence asset forth in SEQ ID NO: 4.

3. The isolated polypeptide of aspect 1 or 2, wherein the polypeptidecomprises 19 repeating units derived from the C-terminal domain of toxinA of Clostridium difficile and 23 repeating units derived from theC-terminal domain of toxin B of Clostridium difficile.

4. The isolated polypeptide of aspect 1, wherein the polypeptide has theamino acid sequence as set forth in SEQ ID NO: 2.

5. The isolated polypeptide of aspect 1, wherein the polypeptide has theamino acid sequence as set forth in SEQ ID NO: 4.

6. A polypeptides comprising an amino acid sequence having at least 85%,more preferably at least 90%, even more preferably at least 95%, mostpreferred 99% sequence identity to the amino acid sequence as set forthin SEQ ID NO: 4.

7. The polypeptide of aspect 6, wherein a hamster vaccinated with saidisolated polypeptide survives intragastric administration of a lethaldose of C. difficile spores at all spore doses (10², 10³ and 10⁴).

8. The polypeptide of aspect 6 or 7, wherein the polypeptide comprises19 repeating units derived from the C-terminal domain of toxin A ofClostridium difficile.

9. The polypeptide of any one of aspects 6 to 8, wherein the polypeptidecomprises 23, 33 or 47 repeating units derived from the C-terminaldomain of toxin B of Clostridium difficile.

10. The polypeptide of any one of aspects 6 to 9, wherein thepolypeptide is selected from the group consisting of SEQ ID: 2, SEQ IDNO: 4, SEQ ID NO. 18, SEQ ID NO: 20 and a polypeptide that is 95%, 96%,97%, 98%, 99% identical to any of SEQ ID: 2, SEQ ID NO: 4, SEQ ID NO.18, or SEQ ID NO: 20.

11. The polypeptide of any one of aspects 6 to 10, wherein thepolypeptide is isolated.

12. The polypeptide of any one of aspects 6 to 11 for use in medicine.

13. The polypeptide of any one of aspects 6 to 11 for the prevention andtreatment of CDAD.

14. The polypeptide of any one of aspects 6 to 11 for the prevention ofCDAD in a subject at risk of a CDAD.

15. The polypeptide of any one of aspects 6 to 11 for the prevention ofCDAD in a subject at risk of a CDAD, wherein said subject at risk ofCDAD is: i) a subject above 65 years of age or a subject below 2 yearsof age; ii) a subject with AIDS; iii) a subject taking or planning totake immunosuppressing drugs; iv) a subject with planned hospitalizationor a subject that is in hospital; v) a subject in or expected to go toan intensive care unit; vi) a subject that is undergoing or is planningto undergo gastrointestinal surgery; vii) a subject that is in orplanning to go to a long-term care such as a nursing home; viii) asubject with co-morbidities requiring frequent and/or prolongedantibiotic use; or ix) a subject with recurrent CDAD.

16. The use of the polypeptide any one of aspects 6 to 11 for themanufacture of a medicament for use in medicine.

17. The use of the polypeptide any one of aspects 6 to 11 for themanufacture of a medicament for the prevention and treatment of CDAD.

18. The use of the polypeptide any one of aspects 6 to 11 for themanufacture of a medicament for the prevention of CDAD in a subject atrisk of a CDAD.

19. The use of the polypeptide any one of aspects 6 to 11 for themanufacture of a medicament for the prevention of CDAD in a subject atrisk of a CDAD, wherein said subject at risk of CDAD is: i) a subjectabove 65 years of age or a subject below 2 years of age; ii) a subjectwith AIDS; iii) a subject taking or planning to take immunosuppressingdrugs; iv) a subject with planned hospitalization or a subject that isin hospital; v) a subject in or expected to go to an intensive careunit; vi) a subject that is undergoing or is planning to undergogastrointestinal surgery; vii) a subject that is in or planning to go toa long-term care such as a nursing home; viii) a subject withco-morbidities requiring frequent and/or prolonged antibiotic use; orix) a subject with recurrent CDAD.

20. A diagnostic kit for detecting a C. difficile infection in a subjectcomprising the polypeptide of any one of aspects 1 to 11.

Preferred Nucleic Acids:

1a. A nucleic acid comprising a nucleotide sequence encoding any of thepolypeptides of any one of aspects 1 to 11.

2a. The nucleic acid of aspect 1a essentially consisting of a nucleotidesequence encoding the polypeptide of any one of aspect 1 to 11.

3a. The nucleic acid of aspect 1a or 2a comprising a nucleotide sequenceselected from the group of SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 17 andSEQ ID NO: 19.

4a. The nucleic acid of aspect 1a or 2a essentially consisting of anucleotide sequence selected from the group of SEQ ID NO: 1, SEQ ID NO:3, SEQ ID NO: 17 and SEQ ID NO: 19.

Preferred Pharmaceutical Compositions:

1c. A pharmaceutical composition comprising the polypeptide of any oneof aspects 1 to 11 or a nucleic acid of any one of aspects 1a to 4a anda pharmaceutically acceptable carrier or excipient.

2c. The pharmaceutical composition of aspect 1c, wherein saidcomposition elicits antibodies neutralizing both C. difficile toxin Aand B.

3c. The pharmaceutical composition of aspect 1c or aspect 2c, whereinsaid composition elicits protective immune response in a subject againstC. difficile toxin A and B.

4c. The pharmaceutical composition of any one of aspects 1c to 3c,further comprising an adjuvant.

5c. The pharmaceutical composition of aspect 4c, wherein the adjuvantcomprises alum.

6c. The pharmaceutical composition of any one of aspects 1c to 5c,further comprising an additional antigen or a drug.

Preferred antibodies: 1d. An antibody directed against a polypeptide ofany of aspects 1 to 11, but not recognizing any of or both C. difficiletoxin A (SEQ ID NO: 6) and B (SEQ ID NO: 8).

Preferred Methods

1e. A method for producing the polypeptide of any one of aspects 1 to 10comprising introducing into a host cell a nucleic acid encoding thepolypeptide, culturing the host cell under conditions that allowexpression of the polypeptide, and isolating the polypeptide.

2e. The method of aspect 1e, wherein the host cell is E. coli.

3e. A method of treating and/or preventing C. difficile associateddisease (CDAD) in a subject comprising administering to a subject inneed thereof the isolated polypeptide of any one of aspects 1 to 11

4e. A method of inducing a specific immune response against both thetoxin A and B of C. difficile in a subject comprising administering thepolypeptide of any one of aspects 1 to 11 to a subject or thepharmaceutical composition of any one of aspects 1c to 6c

5e. A method of preventing a primary disease caused by C. difficileinfection in a subject comprising administering the polypeptide of anyone of aspects 1 to 11 to a subject or the pharmaceutical composition ofany one of aspects 1c to 6c.

6e. A method of preventing a primary disease caused by C. difficileinfection in a subject at risk of C. difficile associated disease(CDAD), wherein said subject at risk of CDAD is: i) a subject above 65years of age or a subject below 2 years of age; ii) a subject with AIDS;iii) a subject taking or planning to take immunosuppressing drugs; iv) asubject with planned hospitalization or a subject that is in hospital;v) a subject in or expected to go to an intensive care unit; vi) asubject that is undergoing or is planning to undergo gastrointestinalsurgery; vii) a subject that is in or planning to go to a long-term caresuch as a nursing home; viii) a subject with co-morbidities requiringfrequent and/or prolonged antibiotic use; or ix) a subject withrecurrent CDAD; comprising administering the polypeptide of any one ofaspects 1 to 11 to said subject or the pharmaceutical composition of anyone of aspects 1c to 6c. 7e. The method of any one of aspects 1e to 6e,wherein the polypeptide or the pharmaceutical composition isadministered to the subject intramuscularly, intradermally,subcutaneously, orally, nasally, or rectally, preferablyintramuscularly.

8e. The method of any one of aspects 1e to 7e, wherein the polypeptideor the pharmaceutical composition is administered to the subject withinat least two doses in a short time interval (weekly or bi-weekly).

9e. A method of detecting C. difficile in a biological sample comprisingcontacting the biological sample with the polypeptide of any one ofaspects 1 to 11 and detecting binding of the polypeptide to thebiological sample, wherein binding of the polypeptide is indicative ofthe presence of C. difficile in the biological sample.

The invention claimed is:
 1. An isolated polypeptide comprising a firstC-terminal portion from Clostridium difficile (C. difficile) toxin A anda second C-terminal portion from C. difficile toxin B, wherein thesecond C-terminal portion from C. difficile toxin B comprises aminoacids 1988-2366 corresponding to SEQ ID NO: 8 and does not compriseamino acids 1834-1967 corresponding to SEQ ID NO:
 8. 2. The isolatedpolypeptide of claim 1, wherein the first C-terminal portion from C.difficile toxin A comprises amino acids 2121-2686 corresponding to SEQID NO:
 6. 3. The isolated polypeptide of claim 1, wherein the firstC-terminal portion from C. difficile toxin A comprises amino acids2276-2710 corresponding to SEQ ID NO:
 6. 4. The isolated polypeptide ofclaim 1, wherein the first C-terminal portion from C. difficile toxin Acomprises amino acids 2276-2686 corresponding to SEQ ID NO:
 6. 5. Theisolated polypeptide of claim 1, wherein the first C-terminal portionfrom C. difficile toxin A does not comprise amino acids 2687-2710corresponding to SEQ ID NO:
 6. 6. The isolated polypeptide of claim 1,wherein the polypeptide comprises at least 19 repeating units derivedfrom the C-terminal domain of C. difficile toxin A.
 7. The isolatedpolypeptide of claim 1, wherein the polypeptide comprises fewer than 23repeating units derived from the C-terminal domain of C. difficile toxinB.
 8. The isolated polypeptide of claim 1, wherein the polypeptide iscapable of inducing neutralizing antibodies against both C. difficiletoxins A and B.
 9. A pharmaceutical composition comprising the isolatedpolypeptide of claim 1 and a pharmaceutically acceptable carrier orexcipient.
 10. The pharmaceutical composition of claim 9, furthercomprising a therapeutic agent selected from the group consisting ofanesthetics, analgesics, anti-inflammatories, steroids, antibiotics,antiarthritics, anorectics, antihistamines and antineoplastics.
 11. Thepharmaceutical composition of claim 9, further comprising an adjuvant.12. The pharmaceutical composition of claim 11, wherein the adjuvantcomprises alum.